Solving a Quadratic Equation by Factorization Method
On selling a ...
Question
On selling a pen at 5% loss and a book at 15% gain Karim gains Rs. 7. If he sells the pen at 5% gain and the book at 10% gain then he gains Rs. 13. The actual price of the book is :
A
Rs. 100
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B
Rs. 80
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C
Rs. 10
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D
Rs. 400
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Solution
The correct option is B Rs. 80 Let the C.P. of the pen be Rs. x and C.P. of he book be Rs. y. Then S.P. of pen at 5% loss =x×95100=RS.95x100 S.P. of book at 15% gain =y×115100= Rs. 115y100 Given, (95x100−x)+(115y100−y)=7
⇒−5x+15y=700
⇒−x+3y=140 or x−3y=−140..........(i) Again S.P. of pen at 5% gain =x×105100=105x100 S.P. of book at 10% gain =y×110100=110y100 Given, (105x100−x)+(110y100−y)=13 ⇒5x+10y=1300
⇒x+2y=260 .........(ii) Subtracting eqn. (i) from eqn (ii), we get (x+2y)−(x−3y)=260+140