Which one of the following interchanges of signs and numbers would make the given equation correct?
9 ÷ 15 × 12 = 20
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → ‘÷’ and ‘×’, 12 and 9
Every option interchanges ÷ and ×, so the expression becomes “first × second ÷ third”. Make the number interchange as well and work from left to right.
Interchanging the signs and 12 with 9 gives 12 × 15 ÷ 9
\(12\times15=180\)
\(180\div9=20\), which equals the right side
Why the other options are incorrect
Option (1) ‘÷’ and ‘×’, 15 and 12 — Incorrect. 9 × 12 ÷ 15 \(=108\div15=\) 7.2, not 20.
Option (2) ‘÷’ and ‘×’, 15 and 9 — Incorrect. 15 × 9 ÷ 12 \(=135\div12=\) 11.25, not 20.
Option (4) None of these — Incorrect. The interchange in Option (3) does balance the equation.