1. **Problem statement:** Alana made a minimum payment of 35 on June 01. After interest was applied, her new balance was 1845.77. We need to find the nominal interest rate compounded daily.
2. **Formula for daily compounding interest:**
$$A = P\left(1 + \frac{r}{n}\right)^{nt}$$
where:
- $A$ is the amount after interest,
- $P$ is the principal (balance after payment),
- $r$ is the nominal annual interest rate (decimal),
- $n$ is the number of compounding periods per year (daily means $n=365$),
- $t$ is the time in years.
3. **Calculate the principal after payment:**
Let the balance before payment be $B$. After paying 35, the balance is $B - 35$.
After one day of interest, the balance is 1845.77.
4. **Set up the equation for one day ($t=\frac{1}{365}$):**
$$1845.77 = (B - 35)\left(1 + \frac{r}{365}\right)^{1}$$
5. **We need $B$ to find $r$. Since $B$ is not given, assume $B = 1845.77$ after interest, so before interest it was $1845.77 / \left(1 + \frac{r}{365}\right)$. But we only have one equation and two unknowns. The problem implies the payment was made before interest, so the balance before interest is $B - 35$.
6. **Rearranged:**
$$\frac{1845.77}{B - 35} = 1 + \frac{r}{365}$$
7. **Assuming the balance before payment is $B = 1845.77 + 35 = 1880.77$ (approximate), then:**
$$\frac{1845.77}{1880.77 - 35} = \frac{1845.77}{1845.77} = 1$$
This is trivial, so we need to consider the interest applied on the balance after payment, meaning the balance before interest is $1845.77 / (1 + r/365)$.
8. **Instead, solve for $r$ using:**
$$1845.77 = (1845.77 - 35)\left(1 + \frac{r}{365}\right)$$
$$1845.77 = 1810.77\left(1 + \frac{r}{365}\right)$$
9. **Divide both sides:**
$$\frac{1845.77}{1810.77} = 1 + \frac{r}{365}$$
$$1.0193 = 1 + \frac{r}{365}$$
10. **Subtract 1:**
$$0.0193 = \frac{r}{365}$$
11. **Multiply both sides by 365:**
$$r = 0.0193 \times 365 = 7.04$$
12. **Convert to percentage:**
$$r = 7.04\%$$ nominal annual interest rate compounded daily.
---
**B) Equivalent annually-compounding rate:**
1. Use the formula for equivalent rates:
$$\left(1 + \frac{r_{daily}}{365}\right)^{365} = 1 + r_{annual}$$
2. Substitute $r_{daily} = 0.0704$:
$$\left(1 + \frac{0.0704}{365}\right)^{365} = 1 + r_{annual}$$
3. Calculate:
$$\left(1 + 0.0001929\right)^{365} \approx e^{0.0704} = 1.0729$$
4. So,
$$r_{annual} = 1.0729 - 1 = 0.0729 = 7.29\%$$
---
**C) Balance on August 01 after payments:**
1. Timeline:
- June 01: payment 35, balance 1845.77 after interest
- July 01: payment 35
- August 01: payment 35
2. Calculate balance on July 01 before payment:
$$B_{July} = (1845.77 - 35)\left(1 + \frac{0.0704}{365}\right)^{30}$$
3. Calculate:
$$B_{July} = 1810.77 \times \left(1 + 0.0001929\right)^{30} = 1810.77 \times 1.0058 = 1821.3$$
4. After July 01 payment:
$$1821.3 - 35 = 1786.3$$
5. Calculate balance on August 01 before payment:
$$B_{Aug} = 1786.3 \times \left(1 + 0.0001929\right)^{31} = 1786.3 \times 1.0060 = 1796.9$$
6. After August 01 payment:
$$1796.9 - 35 = 1761.9$$
---
**D) Three equal payments on Sept 01, Oct 01, Nov 01 to settle debt:**
1. Let each payment be $x$.
2. Balance on Sept 01 before payment:
$$B_{Sept} = 1761.9 \times \left(1 + 0.0001929\right)^{31} = 1761.9 \times 1.0060 = 1772.5$$
3. After Sept 01 payment:
$$1772.5 - x$$
4. Balance on Oct 01 before payment:
$$\left(1772.5 - x\right) \times 1.0060$$
5. After Oct 01 payment:
$$\left(1772.5 - x\right) \times 1.0060 - x$$
6. Balance on Nov 01 before payment:
$$\left[\left(1772.5 - x\right) \times 1.0060 - x\right] \times 1.0060$$
7. After Nov 01 payment, balance is zero:
$$\left[\left(1772.5 - x\right) \times 1.0060 - x\right] \times 1.0060 - x = 0$$
8. Simplify:
$$\left(1772.5 - x\right) \times 1.0060^2 - x \times 1.0060 - x = 0$$
9. Calculate $1.0060^2 = 1.0120$:
$$1772.5 \times 1.0120 - x \times 1.0120 - x \times 1.0060 - x = 0$$
10. Combine $x$ terms:
$$1772.5 \times 1.0120 - x(1.0120 + 1.0060 + 1) = 0$$
11. Calculate:
$$1793.6 - x(3.018) = 0$$
12. Solve for $x$:
$$x = \frac{1793.6}{3.018} = 594.3$$
---
**E) Total interest paid since May 01:**
1. Initial balance on May 01 is unknown, but assume it was $B_0$.
2. Total payments made:
- June 01: 35
- July 01: 35
- August 01: 35
- Sept 01, Oct 01, Nov 01: 3 payments of 594.3 each
3. Total payments:
$$35 + 35 + 35 + 3 \times 594.3 = 105 + 1782.9 = 1887.9$$
4. Final balance after Nov 01 is 0.
5. Interest paid = total payments - initial balance.
6. Initial balance before June 01 payment was approximately:
$$1845.77 + 35 = 1880.77$$
7. Interest paid:
$$1887.9 - 1880.77 = 7.13$$
---
**Final answers:**
- Nominal daily compounded rate: **7.04%**
- Equivalent annual compounded rate: **7.29%**
- Balance on August 01 after payment: **1761.9**
- Three equal payments to settle debt: **594.3** each
- Total interest paid since May 01: **7.13**
Credit Card Interest 4626B7
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