The average of 5 quantities is 6. The average of 3 of them is 8. What is the average of the remaining two numbers?

The average of 5 quantities is 6.

Therefore, the sum of the 5 quantities is 5 *6 = 30.

The average of the 3 of these 5 quantities is 8.

Therefore, the sum of these 3 quantities = 3*8 = 24

The sum of the remaining two quantities = 30 - 24 = 6.

Average of these two quantities = 6 / 2 = 3.

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The age of three children are in proportion 5:7:8. After six years the sum of there ages is 50. Find their ages six years ago. ( in years).

Let there present ages be 5x,7x,8x years respectively.

Then, (5x+6)+(7x+6)+(8x+6)=50

16x=32

x=2

So six years ago their ages was 4,8,10 years respectively.

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