[B].
[C].
[D].
Answer: Option C
Explanation:
The pattern is 1 x 2, 2 x 3, 3 x 4, 4 x 5, 5 x 6, 6 x 7, 7 x 8.
So, the next number is 8 x 9 = 72.
[B].
[C].
[D].
Answer: Option B
Explanation:
Each number is double the preceding one plus 1.
So, the next number is (255 x 2) + 1 = 511.
[B].
[C].
[D].
Answer: Option C
Explanation:
There are two series, beginning respectively with 3 and 7. In one 3 is added and in another 2 is subtracted.
The next number is 1 – 2 = -1.
[B].
[C].
[D].
Answer: Option A
Explanation:
Each number is twice the preceding one with 1 added or subtracted alternatively.
So, the next number is (2 x 261 + 1) = 523.
[B].
[C].
[D].
Answer: Option A
Explanation:
Numbers are all primes. The next prime is 43.
[B].
[C].
[D].
Answer: Option B
Explanation:
Numbers are 13, 23, 33, 43, 53, 63.
So, the missing number is 73 = 343.
[B].
[C].
[D].
Answer: Option C
Explanation:
Numbers are 12, 22, 32, 42, 52, 62, 72.
So, the next number is 82 = 64.
[B].
[C].
[D].
Answer: Option A
Explanation:
Numbers are alternatively multiplied by 2 and increased by 3.
So, the missing number = 61 x 2 = 122.
[B].
[C].
[D].
Answer: Option B
Explanation:
Each number is the proceeding number multiplied by -2.
So, the required number is -128.
[B].
[C].
[D].
Answer: Option D
Explanation:
Prime numbers 2, 3, 5, 7, 11, 13 are to be added successively.
So, 165 is wrong.