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Learn how to solve multiplication equations involving whole numbers using division as the inverse operation. Practice examples are provided to help you understand the concepts easily.
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4 4 Multiplication and division are inverse operations. To solve an equation that contains multiplication, use division to “undo” the multiplication. 4m = 32 Caution ! 4m = 32 4m means “4 m.” m = 8
5 5 ? 5(15)= 75 ? 75 = 75 Additional Example 1A: Solving Multiplication Equations Solve the equation. Check your answer. 5p = 75 p is multiplied by 5. Divide both sides by 5 to undo the multiplication. 5p = 75 p = 15 Check 5p = 75 Substitute 15 forp in the equation. 15 is the solution.
8 8 ? 16 = 8(2) ? 16 = 16 Additional Example 1B: Solving Multiplication Equations Solve the equation. Check your answer. 16 = 8r r is multiplied by 8. 16 = 8r Divide both sides by 8 to undo the multiplication. 2 = r Check 16 =8r Substitute 2 forr in the equation. 2 is the solution.
8 8 ? 8(9)= 72 ? 72 = 72 Check It Out: Example 1A Solve the equation. Check your answer. a is multiplied by 8. 8a = 72 8a = 72 Divide both sides by 8 to undo the multiplication. a = 9 Check 8a = 72 Substitute 9 fora in the equation. 9 is the solution.
3 3 ? 18 = 3(6) ? 18 = 18 Check It Out: Example 1B Solve the equation. Check your answer. w is multiplied by 3. 18 = 3w 18 = 3w Divide both sides by 3 to undo the multiplication. 6 = w Check 18 =3w Substitute 6 forw in the equation. 6 is the solution.
Additional Example 2: Problem Solving Application The area of a rectangle is 56 square inches. Its length is 8 inches. What is its width?
1 Understand the Problem Additional Example 2 Continued The answer will be the width of the rectangle in inches. List the important information: • The area of the rectangle is 56 square inches. • The length of the rectangle is 8 inches. Draw a diagram to represent this information. w 56 8
2 Make a Plan Additional Example 2 Continued You can write and solve an equation using the formula for area. To find the area of a rectangle, multiply its length by its width. A= lw w 56 = 8w l
3 Solve 8 8 Additional Example 2 Continued 56= 8w w is multiplied by 8. 56= 8w Divide both sides by 8 to undo the multiplication. 7= w So the width of the rectangle is 7 inches.
4 Additional Example 2 Continued Look Back Arrange 56 identical squares in a rectangle. The length is 8, so line up the squares in rows of 8. You can make 7 rows of 8, so the width of the rectangle is 7.
Check It Out: Example 2 The area of a rectangle is 48 square inches. Its width is 8 inches. What is its length?
1 Understand the Problem Check It Out: Example 2 The answer will be the length of the rectangle in inches. List the important information: • The area of the rectangle is 48 square inches. • The width of the rectangle is 8 inches. Draw a diagram to represent this information. 8 48 l
2 Make a Plan Check It Out: Example 2 Continued You can write and solve an equation using the formula for area. To find the area of a rectangle, multiply its length by its width. A= lw w 48 = l8 l
3 Solve 8 8 Check It Out: Example 2 Continued 48= 8l l is multiplied by 8. 48= 8l Divide both sides by 8 to undo the multiplication. 6= l So the length of the rectangle is 6 inches.
4 Check It Out: Example 2 Continued Look Back Arrange 48 identical squares in a rectangle. The width is 8, so line up the squares in columns of 8. You can make 6 columns of 8, so the length of the rectangle is 6.