Question

A student multiplied a number by 2/7 instead of 5/7. What is the percentage of error?
1. 45 percent
2. 54 percent
3. 30 percent
4. 60 percent

Answer 1

Correct Answer - Option 4 : 60 percent

Calculation:

Let the number be x.

Actual product = (5/7) × x = 5x/7

Wrong product = (2/7) × x = 2x/7

Percetnage error = (actual product - wrong product)/actual product × 100

Percetnage error = (5x/7 - 2x/7)/(5x/7) × 100 = 3/5 × 100

∴ Percetnage error = 60%