Which number will come next in the following series? 5, 16, 51, 158, ?

Look at the step pattern first. Each term is about three times the previous one, with a small odd number added each time. The additions are 1, 3, 5, so the next addition is 7.

Check: 5 × 3 + 1 = 16; 16 × 3 + 3 = 51; 51 × 3 + 5 = 158; 158 × 3 + 7 = 481. So the answer is D (481).

• A (1454) and C (1452) are far too large. They would need a jump of nearly nine times the previous term, which breaks the pattern.
• B (483) is off by 2. 158 × 3 + 9 = 483 uses 9 instead of the next odd number, 7, so it fits no consistent rule.

Core concept: a mixed series combining multiplication with a patterned addition. In the reasoning paper, the discipline here is to test your hypothesis against every term, not just the first two steps.

Trap: Aspirants check only the first couple of steps and pick an option that looks proportionate, such as B. Always verify the rule on every step before committing.