A shopkeeper sells a mobile phone for Rs. 8107 and makes a profit of 21%. Find the cost of the mobile phone.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Rs. 6700
Profit per cent is reckoned on the cost price: with a 21% profit, the selling price is 121% of the cost. So the cost price is found by dividing the selling price by 1.21; taking 21% off the selling price would work the profit out on the wrong base.
Selling price \(=\frac{121}{100}\times\) cost price
Cost price \(\displaystyle =8107\times\frac{100}{121}=67\times100=\) Rs. 6700, since \(8107=121\times67\)