Explanation:

Let x be the amount deposited at the rate of 15% pa,

Since, the total deposited amount = 25000 rupees,

⇒ The amount deposited at the rate of 18 % pa = (25000 - x) rupees,

Thus, the total interest in one year = 15 % of x + 18 % of (25000 - x)

= 0.15 x + 0.18(25000-x) 

According to the question,

0.15 x + 0.18(25000-x) = 4050

⇒ 0.15x + 4500 - 0.18x = 4050

⇒ -0.03x= 4050 - 4500

⇒ -0.03x = -450

⇒ x = 15000

Hence, option 3 is the correct answer.