SSC CGL 2024 Tier-I · 17 September 2024, Shift 2 · General Intelligence and Reasoning · Question 25 of 100

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.

What will come in place of ‘?’ in the following equation, if ‘+’ and ‘–‘ are interchanged and ‘×’ and ‘÷’ are interchanged? 63 × 9 + 21 – 4 ÷ 5 = ?

(a)5
(b)6
(c)4
(d)7

Answer

Why

Correct — B. Rewrite the line with the symbols swapped, then evaluate the new line under BODMAS.

Rule: + becomes −, − becomes +, × becomes ÷, ÷ becomes ×.

63 × 9 + 21 − 4 ÷ 5 becomes 63 ÷ 9 − 21 + 4 × 5.

63 ÷ 9 = 7
4 × 5 = 20
7 − 21 = −14 → −14 + 20 = 6 → option (b).

Why the others are wrong

(a)
5 — 5 is what the swapped line gives if 63 ÷ 9 comes out as 6. It is 7, since 9 × 7 = 63.
(c)
4 — 4 is what the line gives if the product 4 × 5 is taken as 18, or if the quotient is taken as 5. Both are wrong: the values are 20 and 7.
(d)
7 — 7 is the value of the first term alone, 63 ÷ 9. Picking it means stopping after the division and never doing − 21 + 20.

Concept

Same machinery as any symbol-interchange sum: rewrite, then apply BODMAS to the rewritten line.

What makes this one bite is the negative intermediate. After the swap the ÷ and the × are settled first, giving 7 and 20, and the line becomes 7 − 21 + 20.

Work it left to right at that stage: 7 − 21 = −14, then −14 + 20 = 6. Candidates who refuse to write a negative number move the 21 to the front, as 21 − 7 + 20, and land on 34. Addition and subtraction are done left to right, and the sign carries.

One reshuffle does survive. Signs travel with their terms, so 7 − 21 + 20 is (+7) + (−21) + (+20) and may be written 7 + 20 − 21, which still gives 6.

Moving the bare 21 to the front is a different sum: 21 − 7 + 20 = 34, because that flips the sign on both 21 and 7.

Key facts

After the swap the expression reads 63 ÷ 9 − 21 + 4 × 5.
BODMAS settles 63 ÷ 9 = 7 and 4 × 5 = 20 before the − and the +.
7 − 21 + 20 = 6, by way of the negative intermediate −14.

Study next

Symbol-interchange sums that produce a negative intermediate valueLeft-to-right evaluation of + and − once × and ÷ are settledInterchange items where only one pair of operators is swapped

Common traps

Refusing the negative intermediate. 7 − 21 = −14 is correct, and +20 brings it back to 6.
Evaluating strictly left to right after the swap, which gives −50 and is not on the list.
Answering 7, the value of the first term, after the division goes well and attention drifts.

The instruction sentence is boilerplate and only the expression changes.

Also asked 9 Sep 2024, 09:00, Reasoning Q.8 (5 − 4 ÷ 9 + 80 × 10, keyed 33) and 9 Sep 2024, 09:00, Reasoning Q.1 (4515 × 5 − 431 ÷ 3 + 821, keyed 1375). Reasoning Q.18 in this sitting sets the identical swap on 31 ÷ 3 − 186 × 6 + 17.

Related PYQs

No directly related past PYQ was found.