Quarterly Deposit
1. Stated Problem: Tumi deposits 500 every quarter for 12 years in an account with an 8% annual interest rate compounded quarterly. We want to find the account balance right after the last deposit.
2. Identify variables:
- Quarterly deposit $P = 500$
- Annual interest rate $r = 0.08$
- Quarterly interest rate $i = r / 4 = 0.08 / 4 = 0.02$
- Number of quarters $n = 12 \times 4 = 48$
3. Since deposits happen at the end of each quarter and interest compounds quarterly, the future value of an ordinary annuity formula applies:
$$ FV = P \times \frac{(1+i)^n - 1}{i} $$
4. Substitute the known values:
$$ FV = 500 \times \frac{(1+0.02)^{48} - 1}{0.02} $$
5. Calculate $(1+0.02)^{48}$:
$$ (1.02)^{48} \approx 2.5937424601 $$
6. Compute numerator:
$$ 2.5937424601 - 1 = 1.5937424601 $$
7. Divide by $i$:
$$ \frac{1.5937424601}{0.02} = 79.687123005 $$
8. Multiply by deposit $P$:
$$ 500 \times 79.687123005 = 39843.5615 $$
9. Round to two decimals:
The final amount in the account immediately after the last deposit is approximately $39843.56$.