A person invested a sum of Rs. 9000 at r% per annum at simple interest and a…
2020
A person invested a sum of Rs. 9000 at r% per annum at simple interest and a sum of Rs. 13500 at (r - 4)% at simple interest. If total interest earned on both the investments for 5 years is Rs. 9337.50, then the rate of interest on the first investment is:
- A.
10.2%
- B.
10%
- C.
10.7%
- D.
9.5%
Attempted by 4 students.
Show answer & explanation
Correct answer: C
Key idea: Use the simple-interest formula for both investments and add the interest amounts.
Interest on Rs. 9000 for 5 years at r% = 9000×r×5/100 = 450r.
Interest on Rs. 13500 for 5 years at (r-4)% = 13500×(r-4)×5/100 = 675(r-4).
450r + 675(r-4) = 9337.50, so 1125r = 12037.50 and r = 10.7.
Answer: Option 2, 10.7%, is correct.