A man invested an amount at 10% per annum and another amount at 8% per annum simple interest. Thus, he received Rs.1350 as annual interest. Had he interchanged the amounts invested, he would have received Rs. 45 less as interest. What amounts did he invest at different rates?

Question

Philoid · Accepted Answer

Let the amount invested at 10% per annum and 8% per annum be x and y respectively.

According to question -

Annual Interest on amount x + Annual Interest of amount y = Rs. 1350

⇒ 10x + 8y = 135000

⇒ 5x + 4y = 67500.....(1)

and,

Annual Interest on amount y + Annual Interest of amount x = Rs. 1305

∴

⇒ 8x + 10y = 130500

⇒ 4x + 5y = 65250.....(2)

From equation (1), we get -

x = (67500 - 4y)/5.....(3)

Substituting the value of x in equation (2), we get -

⇒

⇒ (9/5)y = 11250

∴ y = 6250

substituting the value of y in equation (3), we get -

x = 8500

Thus, the amount invested at 10% per annum = Rs. 8500 and,

the amount invested at 8% per annum = Rs. 6250