7th Grade Lesson 8

7th Grade: Lesson 8

Solve Problems with Rational Numbers

Solve using Addition/Subtraction

• A sugar water solution freezes at -1.8 degrees Celsius. A saltwater solution freezes at -13.6 degrees Celsius. What is the difference between the freezing temperature of the sugar-water solution and that of the saltwater solution?

• Estimate to show that your answer is reasonable.

Solve using Multiplication/Division

• Ally, Bobby, and Sarah will share the cost of a cabin rental for a week. Ally agrees to pay 0.3 of the cost. Bobby agrees to pay 0.45 of the cost. Sarah will pay the remaining balance. If the total rental cost is $960, how much will Ally, Bobby, and Sarah each pay towards the week's rent?

Multiple Choice

Which is the best estimate of

 $-\frac{15}{6}\div\ \left(-\frac{1}{2}\right)?$  

• 2

• 1/2

• 0

• -2

Multiple Choice

A scientist measures change in the temperature of a chemical solution. At the start of the experiment, the solution is at a temperature of -14.96 degrees Celsius. The temperature decreases 2.9 degrees Celsius each hour.

What is the temperature of the solution after 3 hours, rounded to the nearest whole degree? Estimate to show your answer is reasonable.

• -20 degrees Celsius

• -24 degrees Celsius

• 0 degrees Celsius

• None of the above

Multiple Select

What is the best estimate of

 $-\frac{15}{16}+\left(-\frac{1}{2}\right)?$  

•  $-1\ \frac{1}{2}$  

•  $-\frac{3}{2}$  

•  $1\ \frac{1}{2}$  

• -1.5

Multiple Choice

Beth plays a video game in which she starts with 0 points. in round 1, she loses 3.5 points; in round 2, she wins 28.5 points; and in round 3, she loses another 3.5 points. What is her final score?

• -18.5

• 18.5

• 21.5

• 35.5