SSC CGL 2025 Tier-I · 14 September 2025, Shift 2 · General Intelligence and Reasoning · Question 22 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 11 September 2026.

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After interchanging + & × and 15 & 30, which of the following equations will hold true?

(a)(15+2)×30=60
(b)(30+3)×15=40
(c)(15+4)×30=135
(d)(30+1)×15=40

Answer

Why

Correct — C. Make both swaps in each option, then work it out.

Rule: + ↔ × and 15 ↔ 30, with the brackets left where they are.

Printed: (15 + 4) × 30 = 135
After the swaps: (30 × 4) + 15
Bracket first: 30 × 4 = 120
Add: 120 + 15 = 135, which matches

So the equation that holds is option (c).

Why the others are wrong

(a)
(15+2)×30=60 — (15+2)×30=60 becomes (30 × 2) + 15 = 60 + 15 = 75, not 60.
(b)
(30+3)×15=40 — (30+3)×15=40 becomes (15 × 3) + 30 = 45 + 30 = 75, not 40.
(d)
(30+1)×15=40 — (30+1)×15=40 becomes (15 × 1) + 30 = 15 + 30 = 45, not 40.

Concept

An interchange item asks you to rewrite each option before judging it. Two swaps happen together here: the signs + and ×, and the numbers 15 and 30.

Make both swaps in a single pass, so a 15 that has just become 30 is not turned back into 15. Brackets are not operators: they stay where they are, so (30 × 4) + 15 is worked bracket first.

Both swaps are needed. Swapping the numbers alone turns option (c) into (30 + 4) × 15 = 510, and swapping the signs alone gives (15 × 4) + 30 = 90. Neither is 135.

Key facts

After the swaps, (15 + 4) × 30 reads (30 × 4) + 15 = 135.
Brackets keep their place when signs and numbers are interchanged.
Both swaps apply at once: 15 becomes 30 and 30 becomes 15 in the same pass.

Study next

Finding which two signs must be interchanged to make an equation trueFinding which two numbers (not digits) must be interchangedSign-substitution items where each sign stands for another

Common traps

Swapping in two passes, 15 → 30 and then every 30 → 15, which turns the new 30s straight back into 15s.
Making one swap and forgetting the other, which gives 510 or 90 for option (c) instead of 135.

The same double swap is set at 12 Sep 2025, 16:00, Reasoning Q.22, with + ↔ × and 3 ↔ 9, where (3+5)×9=48 becomes (9 × 5) + 3 = 48.

Related PYQs

No directly related past PYQ was found.

Topic: Numerical Operations — all 92 SSC CGL questions on it, every solved shift.