Lesson 8.4
1. 2x 5 48
x 5 24
The number is 24.
2. b 2 28 5 35
b 5 35 1 28
b 5 63
There were 63 novels in the school library
at first.
3
3. s 5 24
5
1
s58
5
4.
5.
6.
7.
© Marshall Cavendish International (Singapore) Private Limited.
8.
9.
10.
s 5 40
There are 40 participants in the swimming class.
5h  42
h  8.4
h58
Claire completes 8 laps.
8c  60
c  7.5
c57
The box can hold 7 bundles of comic books.
3y 2 8 5 16
3y 5 16 1 8
y58
The number is 8.
4k 2 k 5 117
3k 5 117
k 5 39
The smaller number is 39.
In 4 years’ time, Shauna will be (d 1 4) years
old and Jason will be (3d 1 4) years old.
d 1 4 1 3d 1 4 5 56
4d 1 8 5 56
4d 5 48
d 5 12 (Shauna)
3d 5 3  12 5 36 (Jason)
Shauna is 12 years old and Jason is
36 years old.
If x dollars is the price of each hat, then each
T-shirt costs (x 1 3) dollars.
6x 1 7(x 1 3) 5 86
6x 1 7x 1 21 5 86
13x 1 21 2 21 5 86 2 21
13x 5 65
x 5 5 (hat)
x 1 3 5 8 (T-shirt)
Mrs. Jones pays $5 for a hat and $8 for
a T-shirt.
Let y the number of teachers needed.
15y  100
2
y6
3
11. Let x be the number of Karen’s lawn chairs.
x 1 2x 1 x 1 3 5 31
4x 1 3 5 31
4x 5 28
x57
Karen has 7 lawn chairs.
12. Let y be the number of dimes Jared has.
0.1y 1 0.25(y 1 8) 5 5.5
0.1y 1 0.25y 1 2 5 5.5
0.35y 1 2 5 5.5
0.35y 5 3.5
y 5 10
Jared has 10 dimes.
Brain @ Work
1. If c is Montell’s present age, then his mother's
present age is (c 1 30).
In 5 years, Montell will be (c 1 5) years old
and his mother will be (c 1 35) years old.
3(c 1 5) 5 c 1 35
3c 1 15 5 c 1 35
3c 1 15 2 15 5 c 1 35 2 15
3c 5 c 1 20
3c 2 c 5 c 2 c 1 20
2c 5 20
c 5 10 (Montell)
10 1 30 5 40
Montell’s mother is 40 years old now.
2. If w inches is the width, then the length
is 2w inches.
The perimeter of the rectangle is
(w 1 2w 1 w 1 2w) 5 6w inches.
6w  74
w  12
1
3
Its maximum width is 12 inches.
Chapter 9
Lesson 9.1
1. P (24, 2)
R (24, 21)
T (0, 23)
V (2, 2)
2.
Q (23, 0)
S (23, 22)
U (7, 22)
W (4, 1)
y
3
W
2
25 24 23 22 21 0
21
U
S
1
22
23
V
1
2 3
4
x
T
Z
24
y57
7 teachers are needed.
Extra Practice Course 1B
(M)MIF_EP6B_Ans.indd 141
141
7/13/11 5:22 PM
y
D
y
16.
5 4 3 2 1 0
1
2
S
3
1
2 3
P
trapezoid
17. a)
y
4
T
3
2
3
1
P
2
5 4 3 2 1 0
1
1
4 3 2 1 0
1
x
4 5
2 3
2
B
A
Q
3
S
y
b)
c)
18. a)
A
4
R
4
Q (22, 23)
T (24, 3)
y
3
6
2
C
1
4 3 2 1 0
1
1
2 3
5
D
4 5 6 7
C
4
x
3
2
2
B
3
1
27 26 25 24 23 22 21 0
21
triangle
1
2 3 4 5
22
y
A
6
R
5
b)
c)
4
S
3
parallelogram
1
2 3
4 5 6 7
isosceles triangle
D (25, 4)
Lesson 9.2
Q
2
1
P
3 2 1 0
1
142
x
2
1
square
5
15.
x
4
4
4
14.
Q
2
1
C
5
3
R
x
1.
2.
3.
4.
5.
AB 5 5 units
CD 5 7 units
EF 5 6 units
GH 5 6 units
JK 5 5 units
23
24
B
x
© Marshall Cavendish International (Singapore) Private Limited.
3.
5.
7.
9.
11.
13.
Quadrant I: Point S
Quadrant II: Point W
Quadrant III: Point U
Quadrant IV: Point Z
Point T lies on the y-axis between
Quadrant III and Quadrant IV.
Point V lies on the x-axis between Quadrant I
and Quadrant IV.
(23, 9)
4. (7, 4)
(5, 26)
6. (28, 22)
(3, 29)
8. (27, 24)
(25, 6)
10. (8, 2)
y-axis
12. x-axis
Answers
(M)MIF_EP6B_Ans.indd 142
7/18/11 4:29 PM