Verified Solution Mathematics Quadratic Equations

A man buys a number of pens for Rs. 60. If he had bought 3 more pens for the same amount, each pen would have cost him Re. 1 less. How many pens did he buy?

9 views 3 helpful Updated Jul 14, 2026
Solution ✔ Verified
  • A10
  • B12
  • C15
  • D18
Explanation

Let the number of pens be x. Original cost per pen = 60/x. If he bought x+3 pens, new cost per pen = 60/(x+3). The equation is 60/x - 60/(x+3) = 1. This simplifies to 60(x+3) - 60x = x(x+3) => 180 = x² + 3x => x² + 3x - 180 = 0. Factoring gives (x+15)(x-12) = 0. Since the number of pens cannot be negative, x = 12.

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