Interest Rate Loan Ed949E
1. **State the problem:**
We are given the initial loan amount and its value after 1 and 2 years. We need to find:
a) The annual rate of interest as a percentage to 1 decimal place.
b) The value of the loan after 10 years, rounded to the nearest penny.
2. **Formula used:**
The loan grows according to compound interest:
$$ A = P(1 + r)^t $$
where:
- $A$ is the amount after $t$ years,
- $P$ is the principal (initial amount),
- $r$ is the annual interest rate (as a decimal),
- $t$ is the time in years.
3. **Find the rate of interest $r$:**
From the data:
- Start: $P = 7500$
- After 1 year: $A = 7920$
Using the formula for $t=1$:
$$ 7920 = 7500(1 + r)^1 $$
Divide both sides by 7500:
$$ 1 + r = \frac{7920}{7500} = 1.056 $$
So,
$$ r = 1.056 - 1 = 0.056 $$
Convert to percentage:
$$ r = 0.056 \times 100 = 5.6\% $$
4. **Check with year 2 data:**
$$ A = 7500(1.056)^2 = 7500 \times 1.115136 = 8363.52 $$
Matches given data, so $r=5.6\%$ is correct.
5. **Calculate loan value after 10 years:**
Using $r=0.056$ and $t=10$:
$$ A = 7500(1.056)^{10} $$
Calculate:
$$ (1.056)^{10} \approx 1.74494 $$
So,
$$ A = 7500 \times 1.74494 = 13087.05 $$
Rounded to nearest penny:
$$ 13087.05 $$
**Final answers:**
- a) Rate of interest per annum = **5.6%**
- b) Value of loan after 10 years = **13087.05** pounds