SSC CGL 2024 Tier-I · 24 September 2024, Shift 3 · General Intelligence and Reasoning · Question 21 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.

What will come in place of the question mark (?) in the following equation, if ‘+’ and ‘–’ are interchanged and ‘×’ and ‘÷’ are interchanged? 1604 × 4 + 87 – 16 ÷ 16 = ?

(a)770
(b)870
(c)570
(d)670

Answer

Why

Correct — C. Rewrite the line with the symbols exchanged, then apply BODMAS.

Given: 1604 x 4 + 87 − 16 ÷ 16
After the swaps: 1604 ÷ 4 − 87 + 16 x 16

1604 ÷ 4 = 401
16 x 16 = 256
401 − 87 = 314
314 + 256 = 570 → option (c)

Why the others are wrong

(a)
770 — 200 above the total. Reaching 770 needs 16 x 16 to come out as 456; the square of 16 is 256, and 314 + 256 = 570.
(b)
870 — 300 above the total. It needs 401 − 87 to be 614, which means starting from 701 — recheck the division, because 1604 ÷ 4 = 401.
(d)
670 — A borrow slip. Reading 401 − 87 as 414 gives 414 + 256 = 670. Do that step on its own: 401 − 87 = 314.

Concept

The instruction changes the symbols, not the numbers, and it changes all of them.

Write the swapped line out first: 1604 ÷ 4 − 87 + 16 x 16. Every + is now −, every − is now +, every x is now ÷ and every ÷ is now x.

Then BODMAS: settle the division and the multiplication (401 and 256), and only then work the plus and minus from left to right.

The four options are spaced 100 apart, so an approximate answer is no answer here. The arithmetic has to be carried exactly, especially the subtraction with a borrow.

Key facts

After the swap the line reads 1604 ÷ 4 − 87 + 16 x 16.
1604 ÷ 4 = 401 and 16 x 16 = 256.
401 − 87 + 256 = 570.
The printed options differ from one another only in the hundreds digit.

Study next

BODMAS applied after a symbol swap, on a line using all four operationsDividing a four-digit number by a single digit accurately under timeInterchange items where only one pair of symbols is exchanged

Common traps

Working the swapped line left to right, before the division and multiplication
Slipping the borrow in 401 − 87 and landing on 670

SSC reuses the same opening term across shifts: 09 Sep 2024, 12:30, Reasoning Q.22 also begins 1604 x 4 and swaps it to 1604 ÷ 4, with different numbers after it. The instruction also runs in this paper at Reasoning Q.17.

Related PYQs

No directly related past PYQ was found.