Multiple choice

A watch is sold for Rs. 144. If the gain percent and the cost price are numerically equal, then what is the cost price of the watch?

  1. Rs. 72

  2. Rs. 80

  3. Rs. 90

  4. Rs. 100
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let CP = x. Gain percent = x. Selling Price = CP + (Gain percent/100) * CP = x + (x/100) * x = 144. x^2 + 100x - 14400 = 0. Factoring gives (x + 180)(x - 80) = 0. Since CP must be positive, x = 80.

AI explanation

Using the profit formula, Selling Price equals Cost Price plus Profit, which translates to 144 = Cost Price + ((Profit Percentage * Cost Price) / 100). Let the cost price and profit percentage both be x, leading to the quadratic equation x + (x^2 / 100) = 144. Solving x^2 + 100x - 14400 = 0 gives the positive value for the cost price and profit percentage as Rs. 80.

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