SSC CGL 2024 Tier-I · 18 September 2024, Shift 1 · General Intelligence and Reasoning · Question 22 of 99

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 6 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Three of the following numbers are alike in a certain way and one is different. Pick the odd one out. (NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding /deleting /multiplying etc., to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

(a)16 – 9 – 139
(b)12 – 7 – 79
(c)17 – 5 – 80
(d)25 – 7 – 175

Answer

Why

Correct — D. Multiply the first two numbers of each triple and compare with the third.

Rule: (first × second) − 5 = third.
16 × 9 = 144, − 5 = 139
12 × 7 = 84, − 5 = 79
17 × 5 = 85, − 5 = 80

Three triples fit exactly. Now the fourth.

25 × 7 = 175, − 5 = 170 — but the triple prints 175.

25 – 7 – 175 is the bare product with nothing subtracted, so it is the one that breaks the shared rule — option (d).

Why the others are wrong

(a)
16 – 9 – 139 — 16 × 9 = 144 and 144 − 5 = 139, exactly as printed. This triple obeys the rule, so it cannot be the odd one out.
(b)
12 – 7 – 79 — 12 × 7 = 84 and 84 − 5 = 79. Its numbers are the smallest on the list, which makes it look different, but the arithmetic is identical.
(c)
17 – 5 – 80 — 17 × 5 = 85 and 85 − 5 = 80. The 5 sitting in second place is a coincidence, not the constant being subtracted.

Concept

An odd-one-out on number triples is settled by one rule that fits three of the four. Start with the plain product of the first two numbers and measure how far the third sits from it.

The gaps here are 144 − 139 = 5, 84 − 79 = 5, 85 − 80 = 5 and 175 − 175 = 0. Three triples share a constant subtraction and the fourth does not, which is the whole question.

Because the rider forbids digit-splitting, you may not rescue 25 – 7 – 175 by reading 175 as separate digits.

The instruction asks for the triple that breaks the rule the other three share, not the one that looks unusual. 12 – 7 – 79 has the smallest numbers on the list and is perfectly regular.

Key facts

Three of the four triples satisfy (first × second) − 5 = third.
The odd triple, 25 – 7 – 175, is the plain product 25 × 7 with nothing subtracted.
The question's rider forbids breaking a number into its digits, so 175 may not be read as 1, 7 and 5.

Study next

Odd-one-out triples built on a product plus or minus a constantNumber-set analogies carrying the same digit-splitting riderTesting a candidate rule against every given item before choosing

Common traps

Multiplying the wrong pair, for instance 9 × 139, and then hunting for a constant.
Choosing 17 – 5 – 80 because a 5 appears in the triple and 5 is the constant subtracted.
Deciding by size, since 175 is the largest third number but size is not the rule.

SSC builds the three wrong options so that each is perfectly regular under the rule, leaving a single break to find. The identical rider and a product-based rule also appear at Reasoning Q.20 of this shift.

Related PYQs

No directly related past PYQ was found.