If the signs ‘+’ and ‘÷’ are interchanged and the signs ‘–’ and ‘×’ are also interchanged, which of the following equations becomes correct?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 24 + 6 – 5 ÷ 3 × 2 = 21
In each option make both interchanges together (+ and ÷ change places, – and × change places), then work out the left side by BODMAS.
Option (1) becomes 24 ÷ 6 × 5 + 3 – 2
\(24\div6\times5=4\times5=20\)
\(20+3-2=21\), which equals the right side
Why the other options are incorrect
Option (2) 36 + 4 × 2 ÷ 7 – 3 = 30 — Incorrect. It becomes 36 ÷ 4 – 2 + 7 × 3 \(=\) 28, not 30.
Option (3) 18 ÷ 9 + 3 – 4 × 5 = 30 — Incorrect. It becomes 18 + 9 ÷ 3 × 4 – 5 \(=\) 25, not 30.
Option (4) 50 + 10 × 1 – 8 ÷ 4 = 52 — Incorrect. It becomes 50 ÷ 10 – 1 × 8 + 4 \(=\) 1, not 52.