A shopkeeper buys a number of books for Rs.1,800. If he had bought 15 more books for the same amount, then each book would have cost him Rs.20 less. Find how many books he bought initially.

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Solution

Q.
A shopkeeper buys a number of books for Rs.1,800. If he had bought 15 more books for the same amount, then each book would have cost him Rs.20 less. Find how many books he bought initially.

Ans.
(30)

Let the number of books bought initially be $x$

According to question, $\frac{1800}{x} - \frac{1800}{x + 15} = 20$

$\Rightarrow x^{2} + 15 x - 1350 = 0$

$\Rightarrow (x + 45) (x - 30) = 0$

$∵$ $x \neq - 45$

$∴$ $x = 30$

So, the number of books bought initially = 30

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