Question

What should come in place of the question mark (?) in the given series? 1155, 1034, 985, 960, 951, ?

• A. 947
• B. 942
• C. 950
• D. 951

Answer 1

Answer:

A. 947

The number that should come in place of the question mark (?) is 947.

The series progresses by subtracting the squares of consecutive odd prime numbers (or consecutive odd numbers in descending order). Let's look at the differences between the consecutive terms:

• 1155 − 1034 = 121 ($11^2$)

• 1034 − 985 = 49 ($7^2$)

• 985 − 960 = 25 ($5^2$)

• 960 − 951 = 9 ($3^2$)

The pattern of subtracted values follows the squares of prime numbers in reverse order ($11^2, 7^2, 5^2, 3^2$). Following this prime number logic, the next prime number down from 3 is 2.

Therefore, the next square to subtract is:

• $2^2$ = 4

• Subtracting 4 from the last term gives the answer:

• 951 − 4 = 947