Illustrative Mathematics Grade 7, Unit 5, Lesson 6: Subtracting Rational Numbers

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Illustrative Math
Grade 7

Lesson 6: Subtracting Rational Numbers

Let’s bring addition and subtraction together.

Illustrative Math Unit 7.5, Lesson 6 (printable worksheets)

Lesson 6 Summary

The following diagram shows how to find the difference between two rational numbers.

Lesson 6.1 Number Talk: Missing Addend

1. Solve each equation mentally.
   248 + c = 458
   c + 43.87 = 58.92
   15/8 + c = 51/8
   
2. Rewrite each addition equation as a subtraction equation.

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Lesson 6.2 Expressions with Altitude

A mountaineer is changing elevations. Write an expression that represents the difference between the final elevation and beginning elevation. Then write the value of the change. The first one is done for you.

Are you ready for more?

Fill in the table so that every row and every column sums to 0. Can you find another way to solve this puzzle?

• Show Answer

  

Can you find another way to solve this puzzle?

• Show Answer

  There is only one way to solve this puzzle because each square can only have one possible value that will fit the condition.

Lesson 6.3 Does the Order Matter?

1. Find the value of each subtraction expression.
   
2. What do you notice about the expressions in Column A compared to Column B?
3. What do you notice about their values?

Lesson 6 Practice Problems

1. Write a sentence to answer each question:
   a. How much warmer is 82 than 40?
   b. How much warmer is 82 than -40?
   
2. A company produces screens of different sizes. Based on the table, could there be a relationship between the number of pixels and the area of the screen? If so, write an equation representing the relationship. If not, explain your reasoning.
   
3. a. What is the difference in height between 30 m up a cliff and 87 m up a cliff? What is the distance between these positions?
   b. What is the difference in height between an albatross flying at 100 m above the surface of the ocean and a shark swimming 30 m below the surface? What is the distance between them if the shark is right below the albatross?
   
4. Find each difference.
   
5. A family goes to a restaurant. When the bill comes, this is printed at the bottom of it:
   How much was the price of the meal? Explain your reasoning.
   
6. Which is a scaled copy of Polygon A? Identify a pair of corresponding sides and a pair of corresponding angles. Compare the areas of the scaled copies.
   

The Open Up Resources math curriculum is free to download from the Open Up Resources website and is also available from Illustrative Mathematics.

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