## Lesson: Using Inverse Operations to Solve Equations

Developing the Concept

Now that students understand how to use inverse operations to solve an equation, they are ready to write and solve equations to find the answer to a word problem.

**Materials:** An overhead transparency with the following problem written on it: *Kayla has two pet snakes, a king snake, and a bull snake. The bull snake is 4 times as long as the king snake. If the king snake is 16 inches long, how long is the bull snake?;* chart paper; copies of Pet Problems (PDF file) Worksheet for each student.

**Preparation:** On chart paper, create a large version of the problem-solving chart shown on the students' *Pet Problems* worksheet. Write the word problem given above on an overhead transparency.

**Prerequisite Skills and Concepts:** Children should know how to write and evaluate algebraic expressions and how to write and solve addition, subtraction, multiplication and division equations using inverse operations. They should also know basic multiplication and division facts.

Begin by reviewing how to use inverse operations to solve *y* x 6 = 54.

(b × 4) x 4 |
= | 16 x 4 |

b |
= | 64 |

b × 4 |
= | 16 |

64 × 4 | = | 16 |

16 | = | 16 |

**Wrap-Up and Assessment**

To see if the students understand how to use inverse operations to solve problems, have them solve the problems on the worksheet. Remind them to analyze each problem by writing the question first, finding the given information, and then writing an equation. Emphasize the need to check each answer. Here are the equations and answers:

- 7
*x*− 2.00 = 7.73;*x*= $1.39 *x*+ 2*x*= 16.05;*x*= $5.35, 2*x*= $10.70- 3(3.95) =
*x;**x*= $11.85

or*x*÷ 3 = 3.95;*x*= $11.85 - 4
*x*+ 5.90 = 14.66;*x*= $2.19 *x*× 4 = 8;*x*= 32 in.