Question

on selling a pen 5% loss and a book at 15% gain A gains 7rs if he sells the pen at 5% gain and the book at 10% gain then he gains 13rs the actual price of the book is?

Answer 1

let the cost of a pen be : Rs P.
let the cost of a book be Rs B.

Loss on selling the pen:  Rs  P * 5/100
Profit on selling the book : Rs  B * 15/100

The overall gain =  15 B/100 -  5 P /100 = Rs 7
                            3 B - P = 140        ---(1)

gain on selling pen : 5 /100 * P
gain on selling book:  10/100 * B
total gain =  5/100 * P + 10/100 *  B =  13
                       P + 2 B = 260    -- (2)

add the two equations above: to get:    5 B = 400
   Price of book = Rs 80
  So price of pen =  3 B - 140 =  Rs 100.  by using (1) above.