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An amount of money at compound interest grows up to ₹ 3,840 in 4 years and up to ₹ 3,936 in 5 years. Find the rate of interest.
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- 2.5%
- 2%
- 3.5%
- 2.05%
Correct Option: A
Here , A1 = ₹ 3,840 , T1 = 4 years and A2 = ₹ 3,936 , T2 = 5 years
Using the given formula , we have
| A = P |  | 1 + |  | T | |
| 100 |
| ∴ 3840 = P | | 1 + | | 4 | ..... (i) | |
| 100 |
3936 = P | | 1 + | | 5 | ..... (ii) | |
| 100 |
Dividing equation (ii) by equation (i),
| = 1 + | ||
| 3840 | 100 |
| ⇒ | = | − 1 | ||
| 100 | 3840 |
| = | = | ||
| 3840 | 3840 |
| ⇒ R = | × 100% = 2.5% | |
| 3840 |
Second Method tom solve this question :
Here, b – a = 5 – 4 = 1 and B = Rs. 3,936, A = Rs. 3,840
| R% = | | − 1 | | × 100% | |
| A |
| R% = | | − 1 | | × 100% | |
| 3840 |
| R% = | | | × 100% | |
| 3840 |
| R% = | × 100% | |
| 3840 |
| R% = | % = 2.5% | |
| 4 |
