After interchanging the signs ‘÷’ and ‘×’ and the numbers 10 and 5, which one of the following becomes a correct equation?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (30 × 10) ÷ 5 = 60
In each option write ‘×’ for ‘÷’, ‘÷’ for ‘×’, 5 for 10 and 10 for 5, then work out the bracket first.
Option (4) becomes (30 ÷ 5) × 10
\(30\div5=6\)
\(6\times10=60\), which equals the right side
Why the other options are incorrect
Option (1) (30 ÷ 5) × 10 = 24 — Incorrect. It becomes (30 × 10) ÷ 5 \(=\) 60, not 24.
Option (2) (10 ÷ 30) × 5 = 70 — Incorrect. It becomes (5 × 30) ÷ 10 \(=\) 15, not 70.
Option (3) (30 ÷ 10) × 5 = 18 — Incorrect. It becomes (30 × 5) ÷ 10 \(=\) 15, not 18.