A sum of 10000 is lent out in two parts, one at 7% simple interest and the other at 12% simple interest. If the annual interest i…

Question

A sum of 10000 is lent out in two parts, one at 7% simple interest and the other at 12% simple interest. If the annual interest is 900, the sum lent at 12% is:

1. A. 3500
2. B. 4000 (Correct answer)
3. C. 4500
4. D. 5000

Correct Answer

Option B — 4000

Detailed Solution & Explanation

The correct answer is `4000.

Key Points

• Let ₹x be lent at 12% and ₹(10000 − x) at 7%, for one year.
• Total simple interest = 0.12x + 0.07(10000 − x) = 900.
• 0.12x + 700 − 0.07x = 900 → 0.05x = 200 → x = ₹4000.
• Set the unknown to the part with the rate you're asked for, write one interest equation, and solve — no need to compute both parts separately.