Which term will replace the question mark (?) in the following series?
Y4, V9, S25, P49, ?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → M121
In a letter-number series the letters and the numbers follow separate rules, so each part is checked on its own.
Letters Y (25), V (22), S (19), P (16): 3 places back each time, so the next letter is \(16-3=13\), M
Numbers 4, 9, 25, 49 are \(2^2, 3^2, 5^2, 7^2\): the squares of the prime numbers 2, 3, 5, 7 in order
The prime after 7 is 11, so the next number is \(11^2=121\)
So the missing term is M121.
Why the other options are incorrect
Option (1) N121 — Incorrect. N is only 2 places back from P, not 3.
Option (2) L64 — Incorrect. L is 4 places back from P, and 64 is \(8^2\), but 8 is not a prime.
Option (3) M64 — Incorrect. The letter is right, but 64 is \(8^2\), and 8 is not a prime, so it breaks the run 2, 3, 5, 7.