### Question: Both A and B sells their watch at the rate of Rs. 5000 per watch. A earned a profit of 25 percent while B incurred a loss of 10 percent. What is the ratio of cost prices of A and B?

- 17:20
- 18:25
- 16:25
- 9:10

Answer: 2. 18:25

Solution:

Creating equations

25 percent profit at a sell of 5000

c.p of A= x

1.25x=5000

10 percent loss at a sell of 5000

c.p of B=y

y-0.1y=5000=0.9 y

ratio of A And B

x/y=5000(0.9)/(1.25 x5000)=9/12.5=90/125

=18/25