3, 4, 7, 7, 13, 13, 21, 22, 31, 34, ?

Answer: Option B

Explanation:

The given sequence is a combination of two series :

I. 3, 7, 13, 21, 31, ? and II. 4, 7, 13, 22, 34

The pattern in I is + 4, + 6, + 8, + 10,.....

The pattern in II is + 3, + 6, + 9, + 12,.....

So, missing term = 31 + 12 = 43.

198, 194, 185, 169, ?

Answer: Option D

The pattern is - 4, - 9, - 16,.....i.e. - 2^{2}, - 3^{2}, - 4^{2},.....

So, missing pattern = 169 - 5^{2} = 169 - 25 = 144.

2, 3, 5,7,11,?, 17

Clearly, the given series consists of prime numbers starting from 2. So, the missing

term is the prime number after 11, which is 13.

6, 12, 21, ?, 48

Answer: Option A

The pattern is + 6, + 9, + 12, + 15, .....

So, missing term = 21 + 12 = 33.

Which term of the series 5, 10, 20, 40, ..... is 1280?

Clearly, 5 x 2 = 10, 10 x 2 = 20, 20 x 2 = 40,.....

So, the series is a G.P. in which a = 5 and r = 2.

Let 1280 be the rath term of the series.

Then, 5x2^{n-1} = 1280 2^{n-1} = 256 = 2^{8} n - 1 = 8 n = 9.