A telephone was sold at 10% loss. If the selling price was Tk 45 more, then there would be a 5% profit. What was the cost (in Tk) of the telephone?

Question: A telephone was sold at 10% loss. If the selling price was Tk 45 more, then there would be a 5% profit. What was the cost (in Tk) of the telephone?

Solution:
Let the cost price be Tk x.

Selling at 10% loss means selling price = x - 10% of x = x - 0.1x = 0.9x.

If the selling price were Tk 45 more, new selling price = 0.9x + 45.

This new selling price gives a 5% profit, so it becomes = x + 5% of x = x + 0.05x = 1.05x.

According to the question,
0.9x + 45 = 1.05x.
⇒ 45 = 1.05x - 0.9x
⇒ 0.15x = 45
⇒ x = 45/0.15
∴ x = 300

Therefore, the cost price of the telephone is Tk 300.