1. 2-8 Division Equations Warm Up Problem of the Day Lesson Presentation
Course 1
Course 1

2. 2-8 Division Equations Warm Up 1. 5x = 20 2. 7n = 84 3. 18 = y – 4
Course 1
Warm Up
Solve.
1. 5x = 20
2. 7n = 84
3. 18 = y – 4
4. 21 = n + 3
x = 4
n = 12
y = 22
n = 18
Course 1

3. Problem of the Day
If 11 is 4 less than 3 times a number, what is the number? 5

4. Learn to solve whole-number division equations.

5. Multiplication is the inverse of division
Multiplication is the inverse of division. When an equation contains division, use multiplication to “undo” the division.

6. Additional Example 1A: Solving Division Equations
Solve the equation. Check your answer. x 7
= 5
x is divided by 7. x 7
= 5
7  x 7
= 7  5
Multiply both sides by 7 to undo the division.
x = 35
Check x 7
= 5 35 7
= 5 ?
Substitute 35 for x in the equation.
5 = 5 ? 
35 is the solution.

7. Additional Example 1B: Solving Division Equations
Solve the equation. Check your answer. p 6
13 =
p is divided by 6. p 6
13 =
6  p 6
6  13 =
Multiply both sides by 6 to undo the division.
78 = p
Check p 6
13 = ? 78 6
13 =
Substitute 78 for p in the equation.
13 = 13 ?
78 is the solution. 

8. Solve the equation. Check your answer. x 2 = 9
Check It Out: Example 1A
Solve the equation. Check your answer. x 2
= 9
x is divided by 2. x 2
= 9
2  x 2
= 2  9
Multiply both sides by 2 to undo the division.
x = 18
Check x 2
= 9 18 2
= 9 ?
Substitute 18 for x in the equation.
9 = 9 ? 
18 is the solution.

9. Solve the equation. Check your answer. p 4 72 =
Check It Out: Example 1B
Solve the equation. Check your answer. p 4
72 =
p is divided by 4. p 4
72 =
4  p 4
4  72 =
Multiply both sides by 4 to undo the division.
288 = p
Check p 4
72 = ?
288 4
72 =
Substitute 288 for p in the equation.
72 = 72 ?
288 is the solution. 

10. height of pine height of aspen = 3
Additional Example 2: Application
At Elk Meadows Park an aspen tree is one-third the height of a pine tree.
height of pine
height of aspen = 3
The aspen tree is 14 feet tall. How tall is the pine tree?
Let h represent the height of the pine tree.
Substitute 14 for height of aspen. h is divided by 3. h 3
14 =
3  h 3
3  14 =
Multiply both sides by 3 to undo the division.
42 = h
The pine tree is 42 feet tall.

11. Jamie’s father weighs 190 pounds.
Check It Out: Example 2
Jamie weighs one-half as much as her father.
father’s weight
Jamie’s weight = 2
Jamie weighs 95 pounds. How many pounds does her father weigh?
Let w represent her father’s weight.
Substitute 95 for Jamie’s weight. w is divided by 2. w 2
95 =
2  w 2
2  95 =
Multiply both sides by 2 to undo the division.
190 = w
Jamie’s father weighs 190 pounds.

12. Lesson Quiz
Solve each equation. Check your answers. x 10
= 7
2. 8 =
= 11
= 7
x = 70 x 4
x = 32 x 9
x = 99 x 15
x = 105
5. The area of Sherry’s flower garden is one- fourth the area of her vegetable garden. The area of the flower garden is 17 square feet. Let x represent the area of her vegetable garden. Find the area of her vegetable garden?
68 square feet