MENTAL MATH – MARCH 11
2
1. 3x = 14
x = 14/3 or 4 or 4.67
2. 4y=22
y = 5.5
5
3
3. x = 5
x=6
4. -12x = 24
x = -2
6
5.
6.
7.
𝑥
4
5
𝑟
= 0.25
x=1
= 2.5
r=2
52
𝑥
=4
x = 13
8.
÷
9. 3x + 7 = 25
x=6
10.2(x + 3) = 4
x = -1
= 18/30 ÷ 2 = 9/30 = 3/10
Homework Review from March 10
p. 301 – 302 #6-11
−5
6. a) 2v =
v=
v=
−5
−5
𝑥
2
2
5
2
x=
1
1
−5
2
12
x =
6
b) =
2
÷
6
(x2 both sides)
4
x2=
5
(÷2 both sides)
6
4
1
3
4
5
c) = -1 a
4
3
−5
=
16
(change to improper fraction)
a
4
(x4 both sides)
= -5a
3
16
÷
3
16
x
3
16
−15
(÷-5 both sides)
−5
1
1
−5
=a
(change division to multiplication)
=a
(simplify)
= a = -1
15
1
1
2
4
d) -1 x = -2
−3
−9
2
4
x=
-3x =
X=
X=
1
2
3
2
(x2)
−18
4
−9
÷
(change to improper fractions)
simplify 
−3
=1
1
1
2
=
−9
2
x
1
−3
−9
2
9
(÷-3)
= (simplify – reduce by multiple of 3)
6
3
𝑥
5
4
7. a) =
12
(x4)
=x
5
(simplify)
2
2 = 2.4 = x
5
−6
b) 2y =
−6
y=
c)
6
−21
6
−7
2
−6
1
5
−4
=

÷
2
÷ =
5
−7
(÷2)
5
3
−7
2
−4
=
1
3
2
10
−7
2
6
x
1
−4
=
−7
−8
7
8
(change to improper fractions)
( x3)
6
21

7
(÷8)
2
7
8
7
2
1
2
1
7
8
16
x =
= 0.4375
8. a) -5.6x = 3.5
3.5
−5.6
= -0.6
= = 0.875 = n
7
W= ÷ =
X=
5
(÷-4)
3
6
−3
= -4n
1
𝑤=
=
(x3)
2
8w =
−6
n
d) 2 w = 1
8
1
x =
(÷-5.6)
= -0.625
Check:
-5.6(-0.625) = 3.5 yup!
b)
𝑒
−2.2
= -0.75
e = -0.75(-2.2) = 1.65
(x-2.2 both sides)
1.65
−2.2
= -0.75 yup
9. a)
ℎ
4.1
= 3.6
(x4.1 both sides)
H = 3.6(4.1) = 14.76
b) 1.472 = 0.46c
1.472
0.46
= c = 3.2
10. a) -5.5 =
1.1
𝑎
-5.5a = 1.1
a=
b)
1.1
=
−5.5
4.8
𝑚
−1
5
6.4
(xa both sides)
(÷-5.5 both sides)
= -0.2
= 6.4
4.8 = 6.4m
4.8
(÷0.46 both sides)
(xm both sides)
(÷6.4 both sides)
3
= m = = 0.75
4
11. a)
2.02
𝑛
= 0.71
2.02 = 0.71n
2.02
0.71
(÷0.71 both sides)
= n = 2.845 = 2.85
b) -7.8 =
−4.3
𝑥
-7.8x = -4.3
X=
(xn both sides)
−4.3
−7.8
= 0.551 = 0.55
(multiply both sides by x)
(divide both sides by -7.8)
WORD PROBLEMS
p. 302 #12 and 13
12) a. s =
𝑑
𝑡
S = 85 km/h
T = 3.75 h
D=?
85 =
𝑑
3.75
(multiply both sides by 3.75)
85 * 3.75 = 318.75 km = d
Pablo traveled 318.75 km.
b. d = 152 km
s = 95 km/h
t=?
95 =
152
𝑡
95t = 152
t=
152
95
(multiply both sides by t)
(divide both sides by 95)
= 1.6 hours
Sheila’s trip took 1.6 hours, or 1 hour and 36 minutes. (60*.6)
13) r = 0.05*n
r = roll, 0.05 = cost of each nickel, n = number of nickels
2 = 0.05n (divide both sides by 0.05) 2/0.05 = 40 = n