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 Rupees 1 less. how many books did he buy ?
Answers
Let the no. of books bought by the shopkeeper be x
therefore, he buys x number of books for rs. 80
cost of x books = 80
cost of 1 book =80/x
if he bought 4 more books
i.e., x+4
so cost of 1 book would be
80/x+4
so it is given that each book had cost 1rs. less
=> 80/x+4 =80/x - 1
=>80/x -80/x+4 =1
=>( 80(x+4) -80x)/x(x+4) =1
=> 80x +320 -80x =x^2 + 4x
=> x^2 + 4x -320=0
so, on solving this quadratic equation
we get the values of x as 16 and -20
so -20 is not possible
therefore, the no. of books bought by the shopkeeper = 16 books
Answer:
VarghesebijupbaxnsHelping Hand
Eq no 1:- total books purchased = x
Therefore unit price = 80/ x
Eq no 2:- 4 extra book purchased on same price = ×+4 =80
Therefore unit price = 80/(×+4)
Difference of price is Rs. 1
Hence 80/× - 80/(x-4) =1
By solving the equation
320/ (xpower2 + 4x)=0
Xpower2+4x-320=0
X(X+20) -16(X+20)=0
(X+20) (X-16)=0
X=-20, X=16
We negate negative answer
Therefore no of books brought =16