In a medical transaction, 17 times the cost price is equal to 8 times the sum of the cost price and the selling price. What is the gain or loss percentage?

Answer: Option A

17 × C.P. = 8(C.P. + S.P.)
17C.P. = 8C.P. + 8S.P.
9C.P. = 8S.P.
C.P. : S.P. = 8 : 9
Profit = 9 - 8 = 1
Profit % = $$\frac{1}{8}$$ × 100 = 12.5%