Comprehensive math worksheet designed to help students practice calculating simple interest and ending balances across 18 different scenarios.

To solve these problems, we use the simple interest formula:

$$
I = P \times r \times t
$$

Where:
- $ I $ = Interest earned
- $ P $ = Principal (initial amount)
- $ r $ = Annual interest rate (as a decimal)
- $ t $ = Time in years

Then, the ending balance is:

$$
\text{Ending Balance} = P + I
$$

We'll go through each problem step by step.

---

1) $35,100 at 4% for 3 years

- $ P = 35,100 $
- $ r = 0.04 $
- $ t = 3 $

$$
I = 35,100 \times 0.04 \times 3 = 4,212
$$
$$
\text{Ending Balance} = 35,100 + 4,212 = \boxed{39,312}
$$

---

2) $150 at 5% for 2 years

- $ P = 150 $
- $ r = 0.05 $
- $ t = 2 $

$$
I = 150 \times 0.05 \times 2 = 15
$$
$$
\text{Ending Balance} = 150 + 15 = \boxed{165}
$$

---

3) $1,400 at 3% for 4 years

- $ P = 1,400 $
- $ r = 0.03 $
- $ t = 4 $

$$
I = 1,400 \times 0.03 \times 4 = 168
$$
$$
\text{Ending Balance} = 1,400 + 168 = \boxed{1,568}
$$

---

4) $450 at 9% for 8 years

- $ P = 450 $
- $ r = 0.09 $
- $ t = 8 $

$$
I = 450 \times 0.09 \times 8 = 324
$$
$$
\text{Ending Balance} = 450 + 324 = \boxed{774}
$$

---

5) $2,400 at 5% for 2 years

- $ P = 2,400 $
- $ r = 0.05 $
- $ t = 2 $

$$
I = 2,400 \times 0.05 \times 2 = 240
$$
$$
\text{Ending Balance} = 2,400 + 240 = \boxed{2,640}
$$

---

6) $600 at 4.5% for 5 months

- $ P = 600 $
- $ r = 0.045 $
- $ t = \frac{5}{12} $ years

$$
I = 600 \times 0.045 \times \frac{5}{12} = 600 \times 0.045 \times 0.4167 \approx 11.25
$$
$$
\text{Ending Balance} = 600 + 11.25 = \boxed{611.25}
$$

---

7) $15,600 at 5.5% for 6 years

- $ P = 15,600 $
- $ r = 0.055 $
- $ t = 6 $

$$
I = 15,600 \times 0.055 \times 6 = 5,148
$$
$$
\text{Ending Balance} = 15,600 + 5,148 = \boxed{20,748}
$$

---

8) $1,300 at 4% for 3 years

- $ P = 1,300 $
- $ r = 0.04 $
- $ t = 3 $

$$
I = 1,300 \times 0.04 \times 3 = 156
$$
$$
\text{Ending Balance} = 1,300 + 156 = \boxed{1,456}
$$

---

9) $750 at 5.5% for 5 years

- $ P = 750 $
- $ r = 0.055 $
- $ t = 5 $

$$
I = 750 \times 0.055 \times 5 = 206.25
$$
$$
\text{Ending Balance} = 750 + 206.25 = \boxed{956.25}
$$

---

10) $850 at 2.2% for 11 months

- $ P = 850 $
- $ r = 0.022 $
- $ t = \frac{11}{12} $

$$
I = 850 \times 0.022 \times \frac{11}{12} \approx 850 \times 0.022 \times 0.9167 \approx 17.12
$$
$$
\text{Ending Balance} = 850 + 17.12 = \boxed{867.12}
$$

---

11) $20,600 at 5.5% for 4 years

- $ P = 20,600 $
- $ r = 0.055 $
- $ t = 4 $

$$
I = 20,600 \times 0.055 \times 4 = 4,532
$$
$$
\text{Ending Balance} = 20,600 + 4,532 = \boxed{25,132}
$$

---

12) $100 at 2% for 9 months

- $ P = 100 $
- $ r = 0.02 $
- $ t = \frac{9}{12} = 0.75 $

$$
I = 100 \times 0.02 \times 0.75 = 1.50
$$
$$
\text{Ending Balance} = 100 + 1.50 = \boxed{101.50}
$$

---

13) $4,000 at 4% for 3 years

- $ P = 4,000 $
- $ r = 0.04 $
- $ t = 3 $

$$
I = 4,000 \times 0.04 \times 3 = 480
$$
$$
\text{Ending Balance} = 4,000 + 480 = \boxed{4,480}
$$

---

14) $7,400 at 2.2% for 9 months

- $ P = 7,400 $
- $ r = 0.022 $
- $ t = \frac{9}{12} = 0.75 $

$$
I = 7,400 \times 0.022 \times 0.75 = 122.10
$$
$$
\text{Ending Balance} = 7,400 + 122.10 = \boxed{7,522.10}
$$

---

15) $1,900 at 6% for 3 years

- $ P = 1,900 $
- $ r = 0.06 $
- $ t = 3 $

$$
I = 1,900 \times 0.06 \times 3 = 342
$$
$$
\text{Ending Balance} = 1,900 + 342 = \boxed{2,242}
$$

---

16) $7,300 at 5.2% for 3 months

- $ P = 7,300 $
- $ r = 0.052 $
- $ t = \frac{3}{12} = 0.25 $

$$
I = 7,300 \times 0.052 \times 0.25 = 94.90
$$
$$
\text{Ending Balance} = 7,300 + 94.90 = \boxed{7,394.90}
$$

---

17) $210 at 5.9% for 3 years

- $ P = 210 $
- $ r = 0.059 $
- $ t = 3 $

$$
I = 210 \times 0.059 \times 3 = 36.93
$$
$$
\text{Ending Balance} = 210 + 36.93 = \boxed{246.93}
$$

---

18) $35,100 at 3.6% for 3 months

- $ P = 35,100 $
- $ r = 0.036 $
- $ t = \frac{3}{12} = 0.25 $

$$
I = 35,100 \times 0.036 \times 0.25 = 315.90
$$
$$
\text{Ending Balance} = 35,100 + 315.90 = \boxed{35,415.90}
$$

---

✔ Final Answers:

| Problem | Ending Balance |
|--------|----------------|
| 1) | $39,312.00 |
| 2) | $165.00 |
| 3) | $1,568.00 |
| 4) | $774.00 |
| 5) | $2,640.00 |
| 6) | $611.25 |
| 7) | $20,748.00 |
| 8) | $1,456.00 |
| 9) | $956.25 |
| 10) | $867.12 |
| 11) | $25,132.00 |
| 12) | $101.50 |
| 13) | $4,480.00 |
| 14) | $7,522.10 |
| 15) | $2,242.00 |
| 16) | $7,394.90 |
| 17) | $246.93 |
| 18) | $35,415.90 |

Let me know if you'd like this formatted as a printable sheet or need explanations for any specific one!