1. **Problem 1: Height of the bottom drawer in a geometric progression**
The height of the drawers forms a geometric progression with first term $a_1=6$ inches and common ratio $r=1.5$. There are 4 drawers.
2. **Formula:** The $n$th term of a geometric sequence is given by
$$a_n = a_1 \times r^{n-1}$$
3. **Calculate the height of the 4th drawer:**
$$a_4 = 6 \times 1.5^{4-1} = 6 \times 1.5^3$$
4. Calculate $1.5^3$:
$$1.5^3 = 1.5 \times 1.5 \times 1.5 = 3.375$$
5. Multiply:
$$a_4 = 6 \times 3.375 = 20.25$$
6. **Answer:** The bottom drawer is 20.25 inches high, which corresponds to option D.
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7. **Problem 2: Chad's salary in year 5 with 3% annual raise**
Initial salary $S_1 = 24000$, raise rate $r = 1 + 0.03 = 1.03$, find salary in year 5.
8. **Formula:** Salary in year $n$ is
$$S_n = S_1 \times r^{n-1}$$
9. Calculate $S_5$:
$$S_5 = 24000 \times 1.03^{4}$$
10. Calculate $1.03^4$:
$$1.03^4 = 1.03 \times 1.03 \times 1.03 \times 1.03 = 1.1255$$ (approx)
11. Multiply:
$$S_5 = 24000 \times 1.1255 = 27012$$ (approx)
12. **Answer:** Chad makes approximately 27012 in year 5, option C.
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13. **Problem 3: Number of stores 18 years after 1987**
Given a geometric sequence with data points:
- Year 1: 60 stores
- Year 8: 215 stores
- Year 9: 258 stores
- Year 14: 642 stores
14. **Find common ratio $r$:**
Using years 1 and 8:
$$a_8 = a_1 \times r^{7}$$
$$215 = 60 \times r^{7}$$
$$r^{7} = \frac{215}{60} = 3.5833$$
15. Take 7th root:
$$r = \sqrt[7]{3.5833} = 1.2$$ (approx)
16. **Find $a_{18}$:**
$$a_{18} = 60 \times 1.2^{17}$$
17. Calculate $1.2^{17}$:
$$1.2^{17} \approx 22.18$$
18. Multiply:
$$a_{18} = 60 \times 22.18 = 1331$$ (approx)
19. **Answer:** The company owned approximately 1331 stores 18 years after 1987, option C.
Geometric Sequences 090F94
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