A shopkeeper buys a number of books for rs 80. if he had bought 4 more books for the same amount , each book would have cost him re 1 less . how many books did he bought ?
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Let the no. of books bought by the shopkeeper be x.
Price of x books = Rs. 80 => Price of 1 book = rs 80/x ...........(i)
Now, if the no. of books had been (x+4)
Price of x+4 books = Rs. 80 => Price of 1 book = Rs 80/ (x+4)...............(ii)
Now, according to the question, (i) - (ii) = 1
i.e 80/x - 80/ (x+4) = 1 => 320/(x2 +4x) = 1
=> x2 +4x - 320 = 0
=> x2 +20x -16x -320 = 0
=> x (x+20) -16 (x+20) = 0
=> (x-16) (x+20) = 0
=> x= 16 or x= -20. But number of books can never be -ve.
Therefore number of books he bought = 16
Hope it helps to you.
Let the no. of books bought by the shopkeeper be x.
Price of x books = Rs. 80 => Price of 1 book = rs 80/x ...........(i)
Now, if the no. of books had been (x+4)
Price of x+4 books = Rs. 80 => Price of 1 book = Rs 80/ (x+4)...............(ii)
Now, according to the question, (i) - (ii) = 1
i.e 80/x - 80/ (x+4) = 1 => 320/(x2 +4x) = 1
=> x2 +4x - 320 = 0
=> x2 +20x -16x -320 = 0
=> x (x+20) -16 (x+20) = 0
=> (x-16) (x+20) = 0
=> x= 16 or x= -20. But number of books can never be -ve.
Therefore number of books he bought = 16
Hope it helps to you.
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