Annuity Comparison
1. **State the problem:** Kiara invests 125 every month for 1 year (12 months) in two different annuities.
- Annuity A: 2% annual interest compounded monthly + 25 bonus (no interest on bonus)
- Annuity B: 3.9% annual interest compounded monthly
We want to find which annuity yields more money after 1 year and by how much.
2. **Calculate future value of Annuity A:**
- Monthly interest rate $i_A = \frac{2\%}{12} = 0.0016667$
- Number of payments $n = 12$
- Monthly payment $P = 125$
- Future value of ordinary annuity formula:
$$FV = P \times \frac{(1+i)^n - 1}{i}$$
Calculate:
$$FV_A = 125 \times \frac{(1+0.0016667)^{12} - 1}{0.0016667}$$
Calculate $(1+0.0016667)^{12}$:
$$ (1.0016667)^{12} \approx 1.0201 $$
So:
$$FV_A = 125 \times \frac{1.0201 - 1}{0.0016667} = 125 \times \frac{0.0201}{0.0016667} = 125 \times 12.06 = 1507.5$$
Add the $25$ bonus (no interest):
$$FV_A^{total} = 1507.5 + 25 = 1532.5$$
3. **Calculate future value of Annuity B:**
- Monthly interest rate $i_B = \frac{3.9\%}{12} = 0.00325$
- Number of payments $n = 12$
- Monthly payment $P = 125$
Calculate:
$$FV_B = 125 \times \frac{(1+0.00325)^{12} - 1}{0.00325}$$
Calculate $(1+0.00325)^{12}$:
$$ (1.00325)^{12} \approx 1.0400 $$
So:
$$FV_B = 125 \times \frac{1.0400 - 1}{0.00325} = 125 \times \frac{0.0400}{0.00325} = 125 \times 12.31 = 1538.75$$
4. **Compare the two annuities:**
Difference:
$$1538.75 - 1532.5 = 6.25$$
5. **Conclusion:**
Annuity B is a better choice; it earns 6.25 more after 1 year.