Worked-out Problems

Chapter 3 continued
30. ––CONTINUED––
Check: 2m 0.5(m 4) 9
2(4.4) 0.5(4.4 4) 9
9 9 ✓
31. 12 2h 0.2(20 6h)
12 2h 4 1.2h
12 3.2h 4
12 4 3.2h 4 4
16 3.2h
16
3.2h
3.
2 3.2
5 h
Check: 12 2h 0.2(20 6h)
12 2(5) 0.2[20 6(5)]
12 12 ✓
32. If w the width, then l w 1.
P 2l 2w
22 2(w 1) 2w
22 2w 2 2w
22 4w 2
22 2 4w 2 2
20 4w
2 0
4 w
4 4
5 w
The width is 5 inches, and the length is 6 inches.
33. P 2l 2w
40 2(x 2) 2(7)
40 2x 4 14
40 2x 18
40 18 2x 18 18
22 2x
2 2
2 x
2 2
11 x
34. P a b c
22 5 x (x 1)
22 2x 6
22 6 2x 6 6
16 2x
1 6
2 x
2 2
8 x
35. P 4s
104 4(x 11)
104 4x 44
104 44 4x 44 44
60 4x
6 0
4 x
4 4
15 x
36. P 2l 2w
32 2(2x 10) 2(x)
32 4x 20 2x
32 6x 20
32 20 6x 20 20
12 6x
1 2
6 x
6 6
2 x
37. a. Let m the total number of minutes you used
last month.
Total
phone
bill
29.50 19.50 0.25(m 200)
b. 29.50 19.50 0.25m 50
29.50 0.25m 30.5
29.50 30.5 0.25m 30.5 30.5
60 0.25m
60
0 .25m
0 .25
0.25
240 m
c. 240 200 40, you used 40 additional minutes
last month.
38. a. 3(x 7) 42
3(x 7)
4 2
3 3
x 7 14
x 7 7 14 7
x 7
3(x 7) 42
3x 21 42
3x 21 21 42 21
3x 21
Charge
Monthly for each
fee
additional
p
minute
3 x
2 1
3 3
Number
of
minutes
over 200
x 7
––CONTINUED––
78 Pre-Algebra
Chapter 3 Worked-Out Solution Key
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