Time, Speed & Distance

Question No 1

In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is

Select the correct answer

3 km/hr 5 km/hr 8 km/hr 9 km/hr

Solution!
Speed in still water
= 1/2(11+5) km/h = 8 km/h.

Question No 2

A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is

Select the correct answer

2 mph 2.5 mph 3 mph 4 mph

Solution!
Let the speed of the stream x mph.

Then,
Speed downstream = (10 + x) mph

Speed upstream = (10 - x) mph

So, [36/(10 - x)] - [36/(10 + x)] = 90/60
(72x)*60 = 90 (100 - x*x)
(x+ 50)(x - 2) = 0

Hence, x = 2 mph..

Question No 3

Two trains are moving in opposite directions at speed of 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train is

Select the correct answer

36 s 45 s 48 s 49 s

Solution!
Relative speed = (60+ 90) km/hr
= 150 * (5/18)m/s
= (125/3)m/s

Distance covered = (1.10 + 0.9) km = 2 km = 2000 m

Hence, Required time = 2000(3/125) = 48 seconds.

Question No 4

A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water?

Select the correct answer

40 minutes 1 hour 1 hr 15 min 1 hr 30 min

Solution!
Rate downstream = (1/10) * 60 km/hr = 6 km/hr

Rate upstream = 2 km/hr

Speed in still water = (1/2)(6 + 2) km/hr = 4 km/hr

Hence, Required time = 5/4 hrs = 1 hr 15 min..

Question No 5

A train is travelling at the speed of 25m/s. In what time will it pass a man sitting on a platform if length of the train is 225 meters?

Select the correct answer

8 sec 9 sec 10 sec 11 sec

Solution!
Speed = v = 25m/s
Length of train = L = 225m

Time = t = L/v
t = 225/25 = 9

Hence train will pass the man in 9 seconds..

Question No 6

The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is

Select the correct answer

200 m 225 m 245 m 250 m

Solution!
Speed = 45 * (5/18)
= 25/2 m/s

Time = 30 sec

Let the length of bridge be x metres

Then,
(130 + x)/30 = 25/2
2(130 + x) = 750

Hence, x = 245 m.

Question No 7

A man rows 1 km upstream in 20 minutes and 1 km downstream in 15 minutes. What is his speed of rowing in still water?

Select the correct answer

2.5 3 3.5 4

Solution!
20 minutes = 20/60 = 1/3 hours
Upstream distance covered in 1/3 hours = 1 Km
Upstream distance covered in 1 hour = 1/(1/3) = 3 Km
Upstream speed = y = 3 Km/h

Now
15 minutes = 15/60 = 1/4 hours
Downstream distance covered in 1/4 hours = 1 Km
Downstream distance covered in 1 hour = 1/(1/4) = 4 Km
Downstream speed = 4 Km/h

speed of rowing = (1/2)*(4+3) = 7/2 = 3.5 Km/h.

Question No 8

Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. The faster train passes the slower train in 36 seconds. The length of each train is

Select the correct answer

50 m 72 m 80 m 82 m

Solution!
Let the length of each train be x metres.

Then, distance covered = 2x metres.

Relative speed = (46 - 36) km/hr
= 10 * (5/18)m/s
= 25/9 m/s
So, 2x/36 = 25/9
= 2x = 100

Hence, x = 50.

Question No 9

A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is

Select the correct answer

4 5 6 10

Solution!
Let the speed of the stream be x km/hr.

Then,
Speed downstream = (15 + x) km/hr

Speed upstream = (15 - x) km/hr

So, [30/(15 + x)] + [30/(15 - x)] = 9/2
900/(225 - x*x) = 9/2

x = 5 km/hr.

Question No 10

A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 140 m long?

Select the correct answer

40 sec 42 sec 45 sec 48 sec

Solution!
Formula for converting from km/hr to m/s is
X km/hr = x * (5/18)m/s

Therefore,
Speed = 45 * (5/18) = 25/2 m/s

Total distance to be covered = (360 + 140) m = 500 m

Formula for finding Time = (Distance/Speed)

Hence, Required time = (500*2)/25
= 40 seconds.

Question No 11

John can swim at the speed of 20 km/h in still water and speed of water is 3 km/h. What is his swimming speed with water?

Select the correct answer

23 km/h 17 km/h 11 km/h 8.5 km/h

Solution!
John's speed in still water = u = 20 Km/h
Speed of water = v = 3 Km/h
John's speed with water = u+v = 20+3 = 23 Km/h.

Question No 12

A man can row 4.5 km an hour in still water but takes twice as long to row up a stream as down it. What is the rate of stream in km/h?

Select the correct answer

1.5 2.25 3 3.75

Solution!
Let rate of stream (speed of water) is x.
Man's speed in still water = u = 4.5 Km/h

Given that
4.5+x = 2(4.5-x)
4.5+x = 9-2x
3x = 4.5
x = 1.5

Hence rate of stream is 1.5 Km/h.

Question No 13

A train 110 meters long passses telegraph pole in 3 seconds. How long will it take to cross a platform 165 meters long?

Select the correct answer

4 sec 4.5 sec 7.5 sec 10 sec

Solution!
Length of the train = L1 = 110m
Time = t1 = 3s

v = L1/t
v = 110/3

Length of the platform = L2 = 165m

t2 = (L1+L2)/v
By putting values
t2 = (110+165)*(3/110)
t2 = 7.5s

Hence it will take 7.5 seconds to cross the platform..

Question No 14

Joseph's speed of rowing in still water is 12 km/h and he finds that it takes him twice as long to row up as to row down the river. Find the speed of water in the river.

Select the correct answer

3.5 km/h 3 km/h 1 km/h 4 km/h

Solution!
Let speed of water is x.
Speed in still water = u = 12 Km/h

As downstream speed is double of upstream speed

(12+x) = 2(12-x)
12+x = 24-2x
3x = 12
x = 4

Hence speed of water is 4 Km/h..

Question No 15

A train running at the speed of 60 km/hr crosses a pole in 9 seconds.What is the length of the train?

Select the correct answer

120 m 180 m 324 m 150 m

Solution!
Speed = 60 * (5/18) = 50/3 m/sec

Length of the train = (Speed x Time) = (50/3) * 9 = 150 meters.

Question No 16

A 100 meters long train can cross a 150 meters long bridge in 20 seconds. What is the speed of the train?

Select the correct answer

10m/s 12.5m/s 15m/s 17.5m/s

Solution!
Length of the train = L1 = 100m
Length of the bridge = L2 = 150m
Time = t = 20s
Speed = v = ?

v = (L1+L2)/t
By putting values
v = (100+150)/20
v = 250/20 = 12.5m/s

Hence speed of train is 12.5m/s..

Question No 17

A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform?

Select the correct answer

120 m 240 m 300 m 100 m

Solution!
Speed = 54 * (5/18)m/s
= 15 m/s

Length of the train = (15 x 20)m = 300 m

Let the length of the platform be x metres

Then,
(x+300)/36 = 15
x + 300 = 540

Hence, x = 240 m.

Question No 18

A goods train runs at the speed of 72 kmph and crosses a 250 m long platform in 26 seconds. What is the length of the goods train?

Select the correct answer

230 m 240 m 260 m 270 m

Solution!
Speed = 72 * (5/18)m/s
= 20 m/s

Time = 26 sec

Let,
the length of the train be x metres

Then,
(x+250)/26 = 20

x + 250 = 520
x = 270.

Question No 19

A ship travels at the speed of 20 km/h upstream and 24 km/h downstream. What is the speed of boat in still water?

Select the correct answer

4 km/h 2 km/h 44 km/h 22 km/h

Solution!
Upstream speed = y = 20 Km/h
Downstream speed = x = 24 Km/h
Speed of ship = (1/2)*(x+y)
=(1/2)*(20+24) = 22 Km/h.

Question No 20

A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds.What is the length of the platform?

Select the correct answer

320 m 350 m 650 m 390 m

Solution!
Speed = (300/18)m/s
= 50/3m/s

Let the length of the platform be x metres

Then, (x+300)/39 = 50/3
3(x + 300) = 1950

Hence, x = 350 m.

Question No 21

A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is

Select the correct answer

48 km/hr 54 km/hr 66 km/hr 82 km/hr

Solution!
Let the speed of the second train be x km/hr.

Relative speed = (x + 50) km/hr
= (x+50)*(5/18) m/s
= (250+5x)18 m/s

Distance covered = (108 + 112) = 220 m

So, 220/[(250 + 5x) /18] = 6
250 + 5x = 660

Hence, x = 82 km/hr.

Question No 22

What is the speed of the train if it crosses a 175 meters long bridge in 41 seconds? Length of the train is 645 meters?

Select the correct answer

54km/h 63km/h 72km/h 81km/h

Solution!
Length of the train = L1 = 645m
Length of the bridge = L2 = 175m
Time = t = 41s
Speed = v = ?

v = (L1+L2)/t
v = (645+175)/41
v = 20m/s = 20 * 18/5 = 72 Km/h

Hence speed of the train is 72 Km/h..

Question No 23

A boat travels at the speed of 25 km/h upstream and 35 km/h downstream. Find the speed of water.

Select the correct answer

7/2 km/h 3/2 km/h 2km/h 5km/h

Solution!
Upstream speed = y = 25 Km/h
Downstream speed = x = 35 Km/h
Speed of water = (1/2)*(x-y)
= (1/2)*(35-35) = 5 Km/h.

Question No 24

A train 110 metres long is running with a speed of 60 kmph. In what time will it pass a man who is running at 6 kmph in the direction opposite to that in which the train is going?

Select the correct answer

5 sec 6 sec 7 sec 10 sec

Solution!
Speed of train relative to man = (60 + 6) km/hr = 66 km/hr.
= 66 * (5/18) = (55/3)m/s

Hence, Time taken to pass the man
= 110 * (3/55) = 6 seconds.

Question No 25

A train is running at a speed of 10 km/h. What will be the distance covered by it in 3 hours?

Select the correct answer

30km 15km 10km 5km

Solution!
As we know that
S=vt (here S is distance, v is speed and t is time). So
distance = 10*3 = 30Km.

Question No 26

A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train?

Select the correct answer

69.5 km/hr 70 km/hr 79 km/hr 79.2 km/hr

Solution!
Let the length of the train be x metres and its speed by y m/sec.

Then,
x/y = 8
x = 8y

Now, (x+264)/20 = y
8y + 264 = 20y
y = 22

Hence, Speed = 22 m/sec
= 22 * (18/5)
= 79.2 km/hr.

Question No 27

A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is

Select the correct answer

250 m 50 m 150 m 200 m

Solution!
Let the length of the train be x metres and its speed by y m/sec.

Then, x/y = 15
y = x/15

So, (x+100)/25 = x/15
15(x + 100) = 25x
15x + 1500 = 25x
1500 = 10x
x = 150 m.

Question No 28

A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.

Select the correct answer

2 hours 3 hours 4 hours 5 hours

Solution!
Speed downstream = (13 + 4) km/hr = 17 km/hr

Time taken to travel 68 km downstream = (68/17)hrs
= 4 hours.

Question No 29

Two trains are running in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then the speed of each train is

Select the correct answer

10 km/hr 18 km/hr 36 km/hr 72 km/hr

Solution!
Let the speed of each train be x m/sec.

Then, relative speed of the two trains = 2x m/sec.

So, 2x = (120 + 120)/12
2x = 20
x = 10

Hence, Speed of each train = 10 m/sec = 10 * (18/5)
= 36 km/hr.

Question No 30

The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is

Select the correct answer

1.2 km 1.8 km 2.4 km 3.6 km

Solution!
Speed downstream = (15 + 3) kmph = 18 kmph

Distance travelled = 18 * (12/60)km = 3.6 km.

Question No 31

A train of length 150 metres is running at the speed of 20m/s. In what time will it cross a 130 metre long bridge?

Select the correct answer

13 sec 14 sec 15 sec 16 sec

Solution!
Length of the train = L1 = 150m
Length of bridge = L2 = 130m
Speed = v = 20m/s

t = (L1 + L2)/v
t = (150+130)/20
t = 14

Hence the train will pass the 130 meter long bridge in 14 seconds..

Question No 32

Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds.If one is moving twice as fast the other, then the speed of the faster train is

Select the correct answer

30 km/hr 45 km/hr 60 km/hr 75 km/hr

Solution!
Let the speed of the slower train be x m/sec

Then,
speed of the faster train = 2x m/sec

Relative speed = (x + 2x) m/sec = 3x m/sec

So, (100+100)/8 = 3x
24x = 200
x = 25/3

So, speed of the faster train = 50/3 m/s
= (50/3 * 18/5)
= 60km/hr.

Question No 33

Anil's swimming speed in still water is 14 km/h and speed of water is 4 km/h. How long will it take him to go upstream 50 km?

Select the correct answer

2.5 hours 5 hours 3 hours 3.5 hours

Solution!
Anil's swimming speed in still water = u = 14 Km/h
Speed of water = v = 4 Km/h
Total upstream speed = u-v = 14-10 = 10 Km/h
Distance to cover = S = 50Km

time = distance/speed
By putting values
time = t = 50/10 = 5 hours.

Question No 34

230 meters long train crosses a man sitting on the platform in 46 seconds. What is the speed of the train?

Select the correct answer

5m/s 10m/s 15m/s 20m/s

Solution!
Length of the train = L = 230m
Time = t = 46s
Speed = v = ?

V = L/t
By putting values
v = 230/46 = 5m/s

Hence speed of the train is 5m/s..

Question No 35

A train travelling at the speed of 10m/s can cross a bridge in 23 seconds. If length of the train is 120 meters. What is length of the bridge?

Select the correct answer

100m 110m 120m 130m

Solution!
Speed = v = 10m/s
Time = t = 23s
Length of train = L1 = 120m
Length of bridge = L2 = ?

t = (L1+L2)/v
By putting values
23 = (120+L2)/10
L2 = 230 - 120 = 110m

Hence bridge is 110m long..

Question No 36

A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train?

Select the correct answer

230 m 240 m 260 m 320 m

Solution!
Relative speed = (120 + 80) km/hr
= 200(5/18)m/s
= (500/9)m/s

Let the length of the other train be x metres

Then,
(x+270)/9 = 500/9
x + 270 = 500

Hence, x = 230.

Question No 37

A boat covers a certain distance downstream in 1 hour, while it comes back in 1.5 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?

Select the correct answer

12 kmph 13 kmph 14 kmph 15 kmph

Solution!
Let the speed of the boat in still water be x kmph.

Then,
Speed downstream = (x + 3) kmph

Speed upstream = (x - 3) kmph

So, (x + 3) * 1 = (x - 3)* 3/2
2x + 6 = 3x - 9

Hence, x = 15 kmph.

Question No 38

If a man takes two hours to row 3 km upstream or 15 km downstream then the speed of current is?

Select the correct answer

1 2 3 4

Solution!
Upstream distance covered in 2 hours = 3Km
Distance covered in 1 hour = 3/2 = `1.5 Km
So,
Upstream speed = 1.5 Km/h
Downstream distance covered in 2 hours = 15Km
Distance covered in 1 hour = 15/2 = 7.5Km

Downstream speed = 7.5 Km/h

Now
Speed of water = (1/2)*(7.5-1.5) = 3 Km/h.

Question No 39

A train is running at the speed of 25 km/h. How far will it travel in 5 hrs?

Select the correct answer

100km 110km 120km 125km

Solution!
Speed = v = 25 Km/h
Time = t = 5h
Distance = S = v*t = 25*5 = 125Km.

Question No 40

A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?

Select the correct answer

4 km/hr 10 km/hr 6 km/hr 8 km/hr

Solution!
Rate downstream = (16/2)km/h = 8 km/h

Rate upstream = (16/4)km/h
= 4 km/h

Hence, Speed in still water = 1/2(8+4)km/h = 6 km/h.

Question No 41

A man can row 1 km upstream in 20 minutes, and downstream in 15 minutes. What is the speed of the current?

Select the correct answer

1 km/h 2 km/h 0.5 km/h 0.25 km/h

Question No 42

David can swim at the speed of 30 km/h in still water and speed of water is 4 km/h. What is his speed of swimming against the direction of water?

Select the correct answer

30 km/h 26 km/h 24 km/h 20 km/h

Solution!
David's speed in still water = u = 30 Km/h
Speed of water = v = 4 Km/h
David's swimming speed against water = u-v = 30-4 = 26 Km/h.

Question No 43

A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is

Select the correct answer

8.5 km/hr 9 km/hr 10 km/hr 12.5 km/hr

Solution!
Man's rate in still water = (15 - 2.5) km/hr
= 12.5 km/hr

Man's rate against the current = (12.5 - 2.5) km/hr
= 10 km/hr.

Question No 44

A man can row down a 10 mile stream in 2 hours and up in 5 hours. What is the average speed in miles per hour?

Select the correct answer

10/7 7/2 20/7 3

Solution!
Downstream distance covered in 2 hours = 10 miles
Downstream distance covered in 1 hour = 10/2 = 5 miles
Downstream speed = 5 mile/h

and
Upstream distance covered in 5 hours = 10 mile
Upstream distance covered in 1 hour = 10/5 = 2 miles

Upstream speed = 2 mile/hr

Average speed = (1/2)*(2+5) = 3.5 mile/hr.

Question No 45

A train 240 m long passes a pole in 24 seconds. How long will it take to pass a platform 650 m long?

Select the correct answer

65 sec 89 sec 100 sec 150 sec

Solution!
Speed = (240/24) = 10m/s

Hence, Required time = (240+650)/10
= 89 seconds.

Question No 46

A train is running at the speed of 70 km/h. How far will it travel in 2.5 hrs?

Select the correct answer

140km 155km 170km 175km

Solution!
Speed = v = 70 Km/h
Time = t = 2.5h
Distance = S = v*t = 70*2.5 = 175Km.

Question No 47

Ali's swimming speed in still water is 18 km/h and speed of water is 6 km/h. How long will it take him to go downstream 72km?

Select the correct answer

3.5 hours 3 hours 4 hours 3.75 hours

Solution!
Ali's swimming speed in still water = u = 18 Km/h
Speed of water = v = 6 Km/h
Total speed down the stream = 18+6 = 24 Km/h

Distance to cover = 72 Km
time = ?

time = distance/speed = time = 72/24 = 3 hours..

Question No 48

A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?

Select the correct answer

2.4 km 2.5 km 3 km 3.6 km

Solution!
Speed downstream = (5 + 1) kmph = 6 kmph

Speed upstream = (5 - 1) kmph = 4 kmph

Let the required distance be x km.

Then,
x/6 + x/4 = 1
2x + 3x = 12
5x = 12

Hence, x = 2.4 km.

Question No 49

What is the length of a bridge if a train of length 550 meters travelling at the speed of 20m/s can cross it in 35 seconds?

Select the correct answer

100m 150m 200m 250m

Solution!
Length of train = L1 = 550m
Speed = v = 20m/s
Time = t = 35s
Length of bridge = L2 = ?

t = (L1+L2)/v
By putting values
35 = (550+L2)/20
700 - 550 = L2
L2 = 150m

Hence length of bridge is 150 meter..

Question No 50

Speed of water in certain river is 6 km/h and it takes a boat four times as long to row up as to row down the river. What is the speed of boat in still water?

Select the correct answer

10 km/h 8 km/h 6 km/h 5 km/h

Solution!
Let speed of boat in still water is x.
Speed of water = v = 6 Km/h
As downstream speed is four times the upstream speed so

(x+6) = 4(x-6)
x+6 = 4x-24
30 = 3x
x = 10

Hence speed of boat in still water is 10 Km/h.

Question No 51

A train 100 meters long crosses a 150 meters long bridge in 25 seconds. What is the speed of the train?

Select the correct answer

27km/h 36km/h 45km/h 54km/h

Solution!
Length of the train = L1 = 100m
Length of the bridge = L2 = 150m
Time = t = 25s

v = (L1+L2)/t
By putting values
v = (100+150)/25
v = 250/25 = 10m/s = 10*(18/5) = 36 Km/h

Hence speed of the train is 36 Km/h..

Question No 52

A train travelling at 36 km/h took 10 seconds to pass a stationary man. What was the length of the train?

Select the correct answer

45m 80m 100m 110m

Solution!
Speed = v = 36 Km/h = 36*(5/18) = 10m/s
Time = t = 10s
Length of the train = L = ?

L = v*t
By putting values
L = 10*10 = 100m

Hence length of the train is 100 meter..

Question No 53

A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is

Select the correct answer

45 km/hr 50 km/hr 54 km/hr 55 km/hr

Solution!
Speed of the train relative to man = (125/10) m/s
= (25/2)m/s
= (25/2) * (18/5)km/hr
= 45 km/hr

Let the speed of the train be x km/hr.
Then,
relative speed = (x - 5) km/hr

x - 5 = 45
Hence, x = 50 km/hr.

Question No 54

A 150m long train is running at the speed of 36km/h. In what time will it pass the 80m long bridge?

Select the correct answer

20 sec 21 sec 22 sec 23 sec

Solution!
Length of train = L1 = 150m
Speed = v = 36 Km/h = 36*(5/18) = 10 m/s
Length of bridge = L2 = 80m

Time = t = (L1 + L2)/v
t = (150+80)/10 = 23

Hence the train will pass the 80 meter long bridge in 23 seconds..

Question No 55

How many seconds will a 500 metre long train take to cross a man walking with a speed of 3 km/hr in the direction of the moving train if the speed of the train is 63 km/hr?

Select the correct answer

25 30 40 45

Solution!
Speed of the train relative to man = (63 - 3) km/hr
= 60 km/hr = 60 * (5/18)m/s
= (50/3)m/s

Hence, Time taken to pass the man
= 500 * (3/50)s
= 30 seconds.

Question No 56

A train travelling at he speed of 72km/h can cross a platform in 17 seconds. If length of the train is 180 meters, what is the length of the platform?

Select the correct answer

160m 170m 180m 190m

Solution!
Speed of train = v = 72Km/h = 72*(5/18) = 20m/s

Time = t = 17s
Length of the train = L1 = 180m
Length of the platform = L2 = ?

t = (L1+L2)/v
By putting values
17 = (180+L2)/20
340-180 = L2
L2 = 160m

Hence length of the platform is 160m..

Question No 57

A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is

Select the correct answer

45 m 50 m 54 m 72 m

Solution!
2 kmph = 2 * (5/18)m/s
= 5/9 m/s

4 kmph = 4 * (5/18)m/s
= 10/9 m/s

Let the length of the train be x metres and its speed by y m/sec.

then, x/[y - (5/9)] = 9
and x/[y - (10/9)] = 10

So, 9y - 5 = x
and 10(9y - 10) = 9x

9y - x = 5
and 90y - 9x = 100

On solving, we get
x = 50

Hence, Length of the train is 50 m..

Question No 58

Speed of water in certain river is 2 km/h and it takes a boat thrice as long to row up as to row down the river. Find the speed of the boat in still water.

Select the correct answer

10 km/h 8 km/h 6 km/h 4 km/h

Solution!
Let speed of boat in still water is x.
Speed of water = v = 2 Km/h

As downstream speed in 3 times the upstream speed so
(x+2) = 3(x-2)
x+2 = 3x-6
8 = 2x
x = 4
Hence speed of boat in still water is 4 Km/h.

Question No 59

A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is

Select the correct answer

130 360 500 540

Solution!
Speed = 78 * (5/18) = 65/3 m/s

Time = 1 minute = 60 seconds

Let the length of the tunnel be x metres

Then,
(800+x)/60 = 65/3
3(800 + x) = 3900

Hence, x = 500.

Question No 60

A man rowing a boat covers an average distance of 7.5 km/h. What is the distance covered after 40 minutes?

Select the correct answer

5 km 10 km 20 km 15 km

Solution!
Distance covered in 60 minutes = 7.5 Km
Distance covered in 1 minute = 7.5/60 = 1/8 Km

Distance covered in 40 minutes = (1/8)*40 = 5 Km.