5.5: Applying Linear Equations to Real-World Problems

I can solve a given problem using a linear equation and record the process.

For each of the following, determine what the linear equation would be. Remember to mirror your equation after y=mx+b, however, the y  and the x may be different variables.

• A phone company charges a flat fee of $20 per month plus $0.10 for every text message sent. Write a linear equation to represent the total monthly cost, 𝐶, in terms of the number of text messages, 𝑡.

• Rina earns $15 per hour babysitting. She also receives a $10 bonus if she works more than 5 hours in a day. Write a linear equation to represent how much she earns, e, after working ℎ, hours (assume she works more than 5 hours).

• A water tank is being filled at a rate of 4 liters per minute. It already contains 10 liters of water. Write a linear equation to represent the volume of water, v, in the tank after 𝑡 minutes.

Throughout this chapter we have looked at:

• identifying the parts of a linear equation

• Graphing linear equations

• solving  linear equations

• recognizing and correcting errors 

and now we will put this all together in linear equation word problems.

As is always recommended, use GRASP to solve the problems. But this time we will also include another math problem solving strategy:

On the poster boards, solve 1 of these equations, have another group check your work. Then solve the remainder of the questions. Be sure to the follow the same format as you have been taught, including all your work, the description of each step, and check your work.