Which two numbers should be interchanged to make the given equation correct?
25 × 7 + 20 – 40 ÷ 4 = 210
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 20 and 40
Interchange the two numbers of each option and work out the left side by BODMAS: division and multiplication first, then addition and subtraction from left to right.
Interchanging 20 and 40 gives 25 × 7 + 40 – 20 ÷ 4
\(20\div4=5\)
\(25\times7=175\)
\(175+40-5=210\), which equals the right side
Why the other options are incorrect
Option (1) 20 and 7 — Incorrect. 25 × 20 + 7 – 40 ÷ 4 \(=500+7-10=\) 497, not 210.
Option (3) 25 and 20 — Incorrect. 20 × 7 + 25 – 40 ÷ 4 \(=140+25-10=\) 155, not 210.
Option (4) 40 and 25 — Incorrect. 40 × 7 + 20 – 25 ÷ 4 \(=280+20-6.25=\) 293.75, not 210.