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Learn to solve whole-number multiplication equations .

Learn to solve whole-number multiplication equations. 4. 4. Multiplication and division are inverse operations. To solve an equation that contains multiplication, use division to “undo” the multiplication. 4 m = 32. Caution !. 4 m = 32. 4 m means “4  m. ”. m = 8. 5. 5. ?.

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Learn to solve whole-number multiplication equations .

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  1. Learn to solve whole-number multiplication equations.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Additional Example 2: Problem Solving Application The area of a rectangle is 56 square inches. Its length is 8 inches. What is its width?

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. Check It Out: Example 2 The area of a rectangle is 48 square inches. Its width is 8 inches. What is its length?

  13. 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

  14. 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

  15. 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.

  16. 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.

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