Compound Interest B299C1
1. **State the problem:** We want to find the values of $A$ and $B$ in the expression $$A \times B^n$$ that models the amount of money in a savings account after $n$ years, given compound interest at 5% per annum.
2. **Given data:**
- Initial amount (start): £600.00
- After 1 year: £630.00
- After 2 years: £661.50
3. **Formula for compound interest:**
$$\text{Amount after } n \text{ years} = A \times B^n$$
where:
- $A$ is the initial amount (principal)
- $B$ is the growth factor per year
4. **Find $A$:**
Since $n=0$ at the start, the amount is $A \times B^0 = A \times 1 = A$.
Therefore, $A = 600$.
5. **Find $B$:**
After 1 year ($n=1$), amount is $630$.
Using the formula:
$$630 = 600 \times B^1 = 600B$$
Divide both sides by 600:
$$B = \frac{630}{600} = 1.05$$
6. **Check with 2 years:**
After 2 years ($n=2$), amount is $661.50$.
Calculate using $A=600$ and $B=1.05$:
$$600 \times (1.05)^2 = 600 \times 1.1025 = 661.5$$
This matches the given data, confirming our values.
**Final answer:**
$$A = 600, \quad B = 1.05$$