Worked-out Problems

Chapter 3 continued
15. x 75 > 125
x 75 75 > 125 75
x > 200
300 200 100 0
16. w 18 < 10
w 18 18 < 10 18
w < 8
t
17. ≥ 3 1 2
t
12 p ≥ 12 p 3 1 2
t ≥ 36
18. 3a 6 ≤ 9
3a 6 6 ≤ 9 6
3a ≤ 3
1
3
a
3
≥ 3
3
a ≥ 1
19. 4(2 d) ≥ 12
8 4d ≥ 12
8 4d 8 ≥ 12 8
4d ≥ 20
4d
≤ 20
4
4
d ≤ 5
20. 2c 5 < 21 2c
2c 5 2c < 21 2c 2c
4c 5 < 21
4c 5 5 < 21 5
4c < 16
6
0 2 4 6 8 10 12
0 12
0 1 2 3 4 5
0 1 2 3 4 5
5
24 36 48 60 72
4 c
< 16
4 4
4
c < 4
3
2
1
6
0
21. Let x the cost of a folder.
Number of folders p Cost of a folder ≤ Total amount
5x ≤ 5.75
5 x
≤ 5. 75
5 5
x ≤ 1.15
You can afford folders that cost $1.15 or less each.
22. 9 ≥ 15 x
9 15 ≥ 15 x 15
6 ≥ x
6 x
≤
1
1
6 ≤ x, orx ≥ 6
23. 8(5 x) < 56
40 8x < 56
40 8x 40 < 56 40
8x < 16
8 x
< 1 6
8 8
x < 2
24. 15 > 3(x 4)
15 > 3x 12
15 12 > 3x 12 12
27 > 3x
2 7
> 3 x
3 3
9 > x, orx < 9
25. 7x 5 ≤ 16
7x 5 5 ≤ 16 5
7x ≤ 21
7 x
≤ 2 1
7 7
x ≤ 3
26. Let x the number of loaves of bread.
Option 1: Make bread
Cost of bread Cost of Number
p 99 0.45x
machine ingredients of loaves
Option 2: Buy bread
Cost of loaf p Number of loaves 2.19x
99 0.45x < 2.19x
99 0.45x 0.45x < 2.19x 0.45x
99 < 1.74x
99
< 1 . 74x
1 .74
1.
74
56.9 < x
You will have to make at least 57 loaves of bread.
108 Pre-Algebra
Chapter 3 Worked-Out Solution Key
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