Single correct option
A dishonest shopkeeper professes to sell his goods at cost price, but he uses a weight of 800 grams for every 1,000 grams (1 kg) he claims to sell. What is his profit percentage?
- A. 20%
- B. 25%
- C. 30%
- D. 33.33%
Show answer and solution
Answer: (B) 25%
For every 1,000 grams he charges for, he actually hands over only 800 grams — so his cost is based on 800 g while his revenue is based on 1,000 g at the same per-gram price.
Profit = extra grams charged for = 1000 − 800 = 200 g, on an actual cost of 800 g.
Profit% = 200/800 × 100 = 25%.
Why others fail: 20% is 200/1000 (using the wrong base — revenue instead of cost); 30% and 33.33% are arithmetic slips.
Tip: For false-weight problems, profit% = (true weight − false weight)/(false weight) × 100 — always divide by what he actually gave, not what he claimed.
Profit = extra grams charged for = 1000 − 800 = 200 g, on an actual cost of 800 g.
Profit% = 200/800 × 100 = 25%.
Why others fail: 20% is 200/1000 (using the wrong base — revenue instead of cost); 30% and 33.33% are arithmetic slips.
Tip: For false-weight problems, profit% = (true weight − false weight)/(false weight) × 100 — always divide by what he actually gave, not what he claimed.
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