Find the solution of h – 18 = 54: 3, 36, 62, or 72.

You can test each number by substituting h in the equation.

COURSE 2 LESSON 2-2COURSE 2 LESSON 2-2

3 – 18 54

– 15 = 54 False

36 – 18 54

18 = 54 False

62 – 18 54

44 = 54 False

72 – 18 54

54 = 54 True

Since the equation is true when you substitute 72 for h, the solution is 72.

2-2

Using Number Sense to Solve Equations

Use mental math to solve each equation.

a. s – 9 = 5

COURSE 2 LESSON 2-2COURSE 2 LESSON 2-2

What you think

What number minus 9 equals 5?

Since 14 – 9 = 5, s = 14.

b. 4z = 28

c. g + 7 = 11 d. = 5c6

What you think

What number times 4 equals 28?

Since 4 • 7 = 28, z = 7.

What you think

What number plus 7 equals 11?

Since 4 + 7 = 11, g = 4.

What you think

What number divided by 6 equals 5?

Since 30 ÷ 6 = 5, c = 30.

2-2

Using Number Sense to Solve Equations

The weight of a packing crate is 14.65 lb. The crate

and its contents together weigh 85.21 lb. Estimate the weight of

the contents.

COURSE 2 LESSON 2-2COURSE 2 LESSON 2-2

14.65 + c = 85.2114.65 15 85.21 85 Choose compatible numbers.

15 + c = 85 What number added to 15 is 85?

c = 70 Use mental math.

The contents of the crate weigh about 70 lb.

Words crate’s plus contents’ equals total weight weight weight

Let c = the weight of the contents.

Equation 14.65 + c = 85.21

2-2

Using Number Sense to Solve Equations

Solve each equation. Use mental math or estimation.

1. q – 15 = 25 2. 6r = 42 3. 17.25 + s = 21.4

4. = 8 5. m – 39.8 = –101.03

q = 40

t = 10

COURSE 2 LESSON 2-2COURSE 2 LESSON 2-2

r = 7 s 4

m –61

80t

2-2

Using Number Sense to Solve Equations