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A clock was sold for $ 144. If the percentage of profit was numerically equal to the cost price, the cost of the clock was
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- $ 72
- $ 80
- $ 90
- $ 100
Correct Option: B
Given that , Selling price of the clock = $ 144
Let the cost price be y.
According to question ,
∴ (100 + y)% of y = 144
⇒ (100 + y)y = 14400
⇒ y2 + 100y – 14400 = 0
⇒ y2 + 180y – 80y – 14400 = 0
⇒ y(y + 180) – 80 (y + 180) = 0
⇒ (y + 180) (y – 80) = 0
⇒ y = 80 [y ≠ –180]
Hence , required answer is $ 80.
