Theory question 102
Commercial Arithmetic(a) A dealer sold a car to a man and made a profit of 15%. The man then sold it to a woman for ₦120,175.00 at a loss of 5%. How much did the dealer buy the car?
(b) The diameter of the wheel of a car is 36 cm. How many revolutions, correct to three significant figures, will it make to cover a distance of 1.05 km? (Take π = 22/7)
Show the model answer
Model answer
(a) The man sold at 95% of his cost: man's cost = 120,175 × 100/95 = ₦126,500.
This is 115% of the dealer's cost: dealer's cost = 126,500 × 100/115 = ₦110,000.00.
(b) Circumference = 22/7 × 36 = 792/7 cm ≈ 113.14 cm.
1.05 km = 105,000 cm. Revolutions = 105,000 ÷ 792/7 = 928.03 ≈ 928 (3 s.f.).
Explanation
Work backwards: a 5% loss means selling price = 95% of cost; a 15% profit means selling price = 115% of cost.