Q. 3 B4.3( 7 Votes )

Represent the following situations mathematically:

A shopkeeper buys a number of books for Rs. 80. If he had bought four more books for the same amount, the book would have cost Re. 1 less.

Answer :

Let ‘x’ be the number of books bought by the shopkeeper.

Cost of one book = Rs. 80 ÷ x.


[ the total cost of books is Rs. 80]


Cost of one book when he buys 4 more books for same rate = Rs. 80 ÷ (x + 4).


When he buys four more books for the same amount; it will cost Re. 1 per book less than the previous.


80 ÷ (x + 4) = (80 ÷ x) − 1



80x = (x + 4) (80 − x)


80x = 80x − x2 + 320 − 4x


x2 + 4x + 320 = 0


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