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### Question

A clerk multiplied a number by 5/4 instead of 4/5. What is the percentage of error?

**A**

36 %.

**B**

38 %.

**C**

34 %.

**D**

40 %.

**Soln.**

**Ans: a**

If the actual figure is x, the error is ${5x}/4$ - ${4x}/5$ = ${5^2x - 4^2x}/{5 × 4}$ = ${9x}/20$, so %-error = ${(9x)/20}/{(5x)/4}$ × 100 = ${9 × 4}/{20 × 5}$ × 100 = 36%.