SSC CGL 2024 Tier-I · 19 September 2024, Shift 1 · General Intelligence and Reasoning · Question 7 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 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 number will come in the place of the question mark (?) in the following equation if ‘+’ and ‘−’ are interchanged and ‘×’ and ‘÷’ are interchanged? 20 + 10 × 2 − 4 ÷ 5 = ?

(a)30
(b)35
(c)40
(d)45

Answer

Why

Correct — B. Rewrite the line with the new symbols first, then solve it normally.

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

20 + 10 × 2 − 4 ÷ 5 becomes 20 − 10 ÷ 2 + 4 × 5

Divide: 10 ÷ 2 = 5
Multiply: 4 × 5 = 20
The line is now 20 − 5 + 20
Left to right: 20 − 5 = 15, then 15 + 20 = 35 -> option (b)

Why the others are wrong

(a)
30 — 30 drops the division: reading the middle term as 20 − 10 = 10 and adding 4 × 5 = 20 gives 30. The ÷ 2 binds to the 10 first, so the subtraction is 20 − 5.
(c)
40 — 40 drops the subtraction instead: 20 + 4 × 5 = 40. After the swap the first operator is a minus, so the 5 from 10 ÷ 2 has to come off the 20.
(d)
45 — 45 is the strict left-to-right run on the rewritten line: 20 − 10 = 10, ÷ 2 = 5, + 4 = 9, × 5 = 45. BODMAS survives the swap — divide and multiply before you add or subtract.

Concept

Symbol-substitution questions test two things in sequence and give marks for neither alone.

First rewrite the expression with the new signs, on paper. Then solve the rewritten line under ordinary BODMAS.

The swap never moves the numbers, so 20, 10, 2, 4 and 5 stay exactly where they are printed. It changes the printed symbols, not the order of precedence: division and multiplication still outrank addition and subtraction after the swap.

Both pairs are interchanged here, so all four operators in the line change. Substituting only one pair is the most common way this item is lost.

Key facts

The rewritten expression is 20 − 10 ÷ 2 + 4 × 5.
Under BODMAS that becomes 20 − 5 + 20, which is 35.
The instruction swaps symbols only, so the operands keep their printed positions.

Study next

Symbol-substitution items where only one pair of operators is interchangedBODMAS on expressions containing both ÷ and ×, worked left to rightItems that also interchange two of the numbers

Common traps

Rewriting the line correctly and then solving it strictly left to right.
Interchanging only one of the two given pairs.
Applying the swap in your head instead of writing the new line out.

SSC states the swap in words and expects the line to be rewritten before it is touched, which is why writing it out is faster than doing it mentally.

A coded-symbol item of a different kind sits at Reasoning Q.2 in this shift (19 Sep 2024, 09:00), where the four symbols stand for family relations.

Related PYQs

No directly related past PYQ was found.