Sheila and her family are driving from Beaumont to west Texas to visit family. They will drive along Interstate 10.

Sheila uses a road map to identify the mile markers for certain towns along the route. Those towns are shown on the map below.

On the map below, click the stars to reveal the name of the city and the mile marker used along the highway for that city. You will use this information in the remaining part of this section.

Read each problem in the interactive below. First, select the operation that you will need. If you are correct, a chalkboard with the word "Correct!" will appear. Click on the chalkboard to see the expression you would use to perform the computation.

Use the information in your interactive to answer these questions. The formula d = rt, where d represents the distance, r represents the rate or speed of travel, and t represents the amount of time traveled, may be helpful.

1. If Sheila’s family drives the posted speed of 80 miles per hour from Junction to Fort Stockton, write an expression Sheila can use to determine the amount of time it will take them to drive from Junction to Fort Stockton.

   Interactive popup. Assistance may be required.

   Need a hint?

   First, you will need to subtract the mile markers to determine the distance traveled. Next, you will need to divide by the speed to determine the time.
   Interactive popup. Assistance may be required.

   Check Your Answer

   d = rt
   (456 − 259) = 80t
   t = (456 − 259) ÷ 80
2. If Sheila’s family drives from Houston to Junction in 41 over 2 1 2 hours, write an expression that Sheila can use to determine their average speed.

   Interactive popup. Assistance may be required.

   Need a hint?

   First, you will need to subtract the mile markers to determine the distance traveled. Next, you will need to divide by the time to determine the speed.
   Interactive popup. Assistance may be required.

   Check Your Answer

   d = rt
   (769 − 456) = r × 41 over 2 1 2
   
   r = (769 − 456) ÷ 41 over 2 1 2
3. Sheila’s mother stopped in San Antonio to fill the vehicle’s fuel tank. The tank holds 22 gallons of gasoline, and the vehicle has a fuel efficiency of 20 miles per gallon. Will Sheila’s mother have enough gasoline to make it to Fort Stockton without stopping to buy more gasoline?

   Interactive popup. Assistance may be required.

   Need a hint?

   First, determine the distance between San Antonio and Fort Stockton by subtracting the mile markers. Next, determine the number of miles that Sheila’s mother will be able to drive from San Antonio by multiplying the number of gallons of gasoline by the fuel efficiency of the vehicle. Compare those two numbers.
   Interactive popup. Assistance may be required.

   Check Your Answer

   Number of Miles to Drive	Number of Miles on Full Tank
   570 − 259 = 311	22 × 20 = 440

   
   
       311 < 440
   
   Number of Miles to Drive < Number of Miles on Full Tank
   Yes, Sheila’s mother will have enough gasoline.

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   Pause and Reflect

   How can you tell which operation you need to perform in a problem?

   Interactive popup. Assistance may be required.

   Check Your Answer

   The action being taken in the problem indicates which operation needs to be performed.

   What actions indicate addition?

   Interactive popup. Assistance may be required.

   Check Your Answer

   If you are combining two or more things, you will need to add.

   What actions indicate subtraction?

   Interactive popup. Assistance may be required.

   Check Your Answer

   If you need to determine the difference between two numbers, such as the difference in location between two mile markers, you will need to subtract.

   What actions indicate multiplication?

   Interactive popup. Assistance may be required.

   Check Your Answer

   When you are scaling a unit rate, you will need to multiply.

   What actions indicate division?

   Interactive popup. Assistance may be required.

   Check Your Answer

   When you are determining a rate or when you are determining a missing factor, you will need to divide.

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   Practice

   1. Savannah is driving from Corpus Christi to Austin for a work meeting. When she left home, the odometer in her car read 14,516.8 miles. When she arrived in Austin, the odometer read 14,737.3 miles. Savannah drove for exactly 3 hours from home to her meeting. Write an expression to determine Savannah’s average speed.

      Interactive popup. Assistance may be required.

      Need a hint?

      Average speed is a ratio of the number of miles driven to the amount of time required to complete the drive.
      Interactive popup. Assistance may be required.

      Check Your Answer

      (14,737.3 − 14,516.8) ÷ 3
   2. The chart below shows the low temperatures for five cities during a recent January.
      

      Write an expression that you could use to determine the mean low temperature for this set of cities.

      Interactive popup. Assistance may be required.

      Need a hint?

      How can you calculate the mean of a set of numbers?
      Interactive popup. Assistance may be required.

      Check Your Answer

      [-4.5 + (-3.1) + (-2.8) + 0.4 + (-1.3)] ÷ 5
   3. A recipe calls for 11 over 4 1 4 cups of sugar, and Isabella wants to make 3 batches of the recipe. She currently has 6 cups of sugar in the canister. Write an expression that Isabella can use to determine how much sugar will remain after she has made all 3 batches of the recipe.

      Interactive popup. Assistance may be required.

      Need a hint?

      What actions are being done to the initial 6 cups of sugar?
      Interactive popup. Assistance may be required.

      Check Your Answer

      6 − (3 × 11 over 4 1 4 )