At what rate percent compound interest per annum will 640 amount to Rs 774.40 in 2 years?

Explanation

To find the rate percent of compound interest per annum that will cause Rs. 640 to amount to Rs. 774.40 in 2 years, we can use the formula for compound interest.

### Step-by-Step Solution:

1. **Identify the variables:**
- Principal (P) = Rs. 640
- Amount (A) = Rs. 774.40
- Time (n) = 2 years
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