Prelims 2024

Q. What will come in place of * in the sequence 3, 14, 39, 84, *, 258?

a) 150
b) 155
c) 160
d)176
Correct answer: b) 155

Question from UPSC Prelims 2024 CSAT Paper

Explanation:

The sequence follows a specific pattern based on the hint provided. Each number in the sequence is the sum of a number (n), its square (n²), and its cube (n³), where n starts at 1 and increases by 1 for each term.

Let’s break down each term in the sequence:

1. 3 = 1 + 1² + 1³ = 1 + 1 + 1 = 3
2. 14 = 2 + 2² + 2³ = 2 + 4 + 8 = 14
3. 39 = 3 + 3² + 3³ = 3 + 9 + 27 = 39
4. 84 = 4 + 4² + 4³ = 4 + 16 + 64 = 84
5. * (the missing term) = 5 + 5² + 5³ = 5 + 25 + 125 = 155
6. 258 = 6 + 6² + 6³ = 6 + 36 + 216 = 258

As we can see, the missing term (*) corresponds to n = 5 in the pattern.

Therefore, the number that should replace * in the sequence is 155, which matches option b) in the given choices.

UPSC All In One App
Get UPSC Prelims PYQ, Mains Model Answer, Test Series, Short Notes. Click to Install !!