SSC CGL 2024 Tier-I · 25 September 2024, Shift 2 · 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 10 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.

Which two numbers (not digits) should be interchanged to make the given equation correct? 15 + 5 × 8 – 72 ÷ 4 + 16 × 3 = 101

(a)15 and 16
(b)5 and 4
(c)8 and 4
(d)5 and 3

Answer

Why

Correct — D. Evaluate the equation as printed, under BODMAS:

5 x 8 = 40, 72 / 4 = 18, 16 x 3 = 48
15 + 40 - 18 + 48 = 85, not 101.

Now interchange 5 and 3, giving 15 + 3 x 8 - 72 / 4 + 16 x 5:

3 x 8 = 24
72 / 4 = 18
16 x 5 = 80
15 + 24 - 18 + 80 = 101 -> option (d).

Why the others are wrong

(a)
15 and 16 — Interchanging 15 and 16 gives 16 + 5 x 8 - 72 / 4 + 15 x 3 = 16 + 40 - 18 + 45 = 83.
(b)
5 and 4 — Interchanging 5 and 4 gives 15 + 4 x 8 - 72 / 5 + 16 x 3, and 72 / 5 is not even whole. The total is 80.6.
(c)
8 and 4 — Interchanging 8 and 4 gives 15 + 5 x 4 - 72 / 8 + 16 x 3 = 15 + 20 - 9 + 48 = 74.

Concept

These are BODMAS items dressed as puzzles. No operator changes; two printed numbers trade places and the expression is then evaluated the ordinary way, multiplication and division before addition and subtraction.

Work out the printed value once. Here it is 85, which is 16 short of 101.

A swap only alters the terms the two numbers stand in, so hunt for a pair that moves exactly that much: 5 and 3 sit in 5 x 8 and 16 x 3, worth 40 and 48, and after the swap they are worth 24 and 80 - a net gain of 16.

The rider numbers, not digits means 15, 16 and 72 travel whole. You may never pull the 1 out of 15 or the 7 out of 72.

Key facts

As printed the expression equals 85, from 15 + 40 - 18 + 48.
Interchanging 5 and 3 gives 15 + 24 - 18 + 80 = 101.
The swap leaves BODMAS untouched, so multiplication and division still resolve first.

Study next

Interchange-two-numbers equations evaluated under BODMASInterchange-two-signs equations, the same item with the operators movedTesting a candidate swap by its net change instead of re-evaluating in full

Common traps

Evaluating strictly left to right and starting from the wrong value
Swapping digits inside 15, 16 or 72, which the stem forbids
Settling for a swap that repairs one term while breaking another

The same stem, rider and all, recurs across the 2024 papers - see 11 Sep 2024, 09:00, Reasoning Q.1 and 18 Sep 2024, 16:00, Reasoning Q.8. The sign-interchange twin sits at Reasoning Q.2 of this shift.

Related PYQs

No directly related past PYQ was found.