A person sold a book at a gain of 15%. Had he bought it for 25% less and sold it for Tk. 600 less, he would have made a profit of 32%. The cost price of the book was:

Question: A person sold a book at a gain of 15%. Had he bought it for 25% less and sold it for Tk. 600 less, he would have made a profit of 32%. The cost price of the book was:

Solution:
Let the original cost price = Tk. x

Selling price = x + 15% of x
= 115x/100
= 23x/20

Cost price = x - 25% of x
= x - (25x/100)
= 75x/100
= 3x/4

Selling price = (3x/4) + 32% of (3x/4)
= (3x/4) + (32/100) × (3x/4)
= 99x/100

ATQ,
(23x/20) - (99x/100) = 600
⇒ (115x - 99x)/100 = 600
⇒ 16x = 600 × 100
⇒ x = (600 × 100)/16
∴ x = 3750