Two mobile phones were purchased at the same price. One was sold at a profit of 20% and the second was sold at a price which was Rs.1520 less than the price at which the first was sold. If the overall profit earned by selling both the mobile phones was 1%, then determine the cost price of one mobile?

Rs. 4000

The correct answer is Option (2) → Rs. 4000

Let the cost price of each mobile be Rs. x.
So, total cost price of two mobiles = 2x.

First mobile is sold at a profit of 20 percent.
Selling price of first mobile = x + 20 percent of x = 1.2x.

Second mobile is sold at a price Rs. 1520 less than the first.
Selling price of second mobile = 1.2x − 1520.

Total selling price of both mobiles = 1.2x + (1.2x − 1520) = 2.4x − 1520.

Overall profit is 1 percent on total cost price.
Total cost price = 2x, so total selling price = 2x + 1 percent of 2x = 2.02x.

Equating selling prices:
2.4x − 1520 = 2.02x
0.38x = 1520
x = 4000