Which two numbers need to be swapped to make this equation correct? 20÷5×3 + 10 − 4 = 20

Question

Which two numbers need to be swapped to make this equation correct? 20÷5×3 + 10 − 4 = 20

1. A. 20 and 10
2. B. 3 and 4
3. C. 4 and 5 (Correct answer)
4. D. 5 and 10

Correct Answer

Option C — 4 and 5

Detailed Solution & Explanation

The correct answer is 4 and 5.

Key Points

• As printed, 20 ÷ 5 × 3 + 10 − 4 evaluates to:
  • 20 ÷ 5 = 4, 4 × 3 = 12, 12 + 10 = 22, 22 − 4 = 18, not 20.
• Swapping 4 and 5 gives 20 ÷ 4 × 3 + 10 − 5:
  • 20 ÷ 4 = 5, 5 × 3 = 15, 15 + 10 = 25, 25 − 5 = 20 ✓

Additional Information

• Test each option by substitution rather than reasoning abstractly — with only four candidates it is faster and certain.
• BODMAS still governs after the swap: division and multiplication before addition and subtraction, each pair left to right.
• A useful filter is to check whether a swap changes the divisibility. Here 20 ÷ 4 stays whole, whereas swapping 20 and 10 would give 10 ÷ 5 × 3 and a very different scale.
• Only the numbers move in this question type; the operators stay where they are, which distinguishes it from operator-substitution questions.