Pawan multiplied a number by 2/5 instead of 5/2, what is the percentage error in the calculation?

Question

A shopkeeper sells his goods at cost price but uses a weight of 860 gm instead of kilogram weight.
What is his profit percentage?

Answer 1

[X((5/2) - (2/5))]/[X(5/2)] × 100
= [(25 - 4)/10]/[(5/2)] ×100
= 42/50 × 100
= 84% error.