In following questions, a sequence of groups of alphabets and numbers is provided with one term missing , Choose the missing term from options. 2A11, 4D13, 12G17, ?

The first numbers in the terms follow the sequence x 2, x 3, x 4.The middle letter of each term is moved three steps forward to obtain the corresponding letter of the next term>The last numbers follow the sequence + 2, + 4, + 6.

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In following number series, either one term is missing or is incorrect. Choose correct answer from options

Choose correct answer from options 1, 2, 5, 10, 17, 28

Choose correct answer from options 1, 2, 5, 10, 17, 28

The correct sequence is + 1, + 3, + 5, + 7, + 9.

So, 28 is wrong and must be replaced by (17 + 9) i.e. 26..

The sum of how many terms of the series 6 + 12 + 18 + 24 + ... is 1800 ?

This is an A.P. in which a = 6, d = 6 and Sn = 1800

Then, n/2[2a + (n - 1)d] = 1800

n/2[2 x 6 + (n - 1) x 6] = 1800

3n (n + 1) = 1800

n(n + 1) = 600

n2 + n - 600 = 0

n2 + 25n - 24n - 600 = 0

n(n + 25) - 24(n + 25) = 0

(n + 25)(n - 24) = 0

n = 24

Number of terms = 24.

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(22 + 42 + 62 + ... + 202) = ?

(22 + 42 + 62 + ... + 202) = (1 x 2)2 + (2 x 2)2 + (2 x 3)2 + ... + (2 x 10)2

= (22 x 12) + (22 x 22) + (22 x 32) + ... + (22 x 102)

= 22 x [12 + 22 + 32 + ... + 102] Ref: (12 + 22 + 32 + ... + n2) =1/6 n(n + 1)(2n + 1)

=(4 x 1/6x 10 x 11 x 21)

= (4 x 5 x 77)= 1540.

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