A dishonest shopkeeper professes to sell his goods at cost price but uses a false weight of 920 grams for a 1 kg weight. What is his overall profit percentage?
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For dishonest dealing with false weights, remember the trick:
Profit % = $\frac{\text{Error}}{\text{Weight Used} - \text{Error}} \times 100$.
Error = $1000 - 920 = 80$ grams.
Weight Used = 920 grams.
Profit % = $\frac{80}{920} \times 100 = 8.69\%$.