SSC CHSL 10 Jan 2017 Shift 3 Paper

Let the number be 40
When the student multiplied it by 5/8, ⇒ original result = $\frac{5}{8}\times 40=25$
When the student multiply it by 8/5, ⇒ New result = $\frac{8}{5}\times 40=64$
⇒ Percentage error in calculation = $\frac{\left(64-25\right)}{64}\times 100$
= $\frac{3900}{64}=$ 60.937 ≈ 60.94%