Envision Math 2.0: Grade 7, Volume 1
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Review

Exercise 3 Page 76

Practice makes perfect
When multiplying real numbers, the product will be positive if the signs are the same and it will be negative if the signs are different. cc Same Sign & Different Signs (+)(+)=(+) & (+)(-)=(-) (-)(-)=(+) & (-)(+)=(-)In our case both numbers are negative, so the product will be positive.
- 7* - 14
7 * 14
98
We can verify this using a calculator.
Error creating thumbnail: Unable to save thumbnail to destination
When multiplying real numbers, the product will be positive if the signs are the same and it will be negative if the signs are different. cc Same Sign & Different Signs (+)(+)=(+) & (+)(-)=(-) (-)(-)=(+) & (-)(+)=(-)In our case one number is positive and one number is negative, so the product will be negative.
- 15* 12
- 180
We can verify this using a calculator.

Extra

Properties of Operations
Some important properties that can help us understand why the multiplication of real numbers works the way that it does are the Associative Property of Multiplication and the Commutative Property of Multiplication. rc Associative Property:& (a* b)* c=a* (b* c) Commutative Property:& a* b = b * a Let's look at how the Associative Property can help us understand the given exercise.
- 15 * 12
(-1 * 15) * 12
-1* (15*12)
-1 * 180
- 180
When multiplying real numbers, the product will be positive if the signs are the same and it will be negative if the signs are different. cc Same Sign & Different Signs (+)(+)=(+) & (+)(-)=(-) (-)(-)=(+) & (-)(+)=(-)In our case one number is positive and one number is negative, so the product will be negative.
9* - 20
- 9 * 20
- 180
We can verify this using a calculator.
Error creating thumbnail: Unable to save thumbnail to destination
<ebox title="Properties of Operations" type="extra"> Some important properties that can help us understand why the multiplication of real numbers works the way that it does are the Associative Property of Multiplication and the Commutative Property of Multiplication. rc Associative Property:& (a* b)* c=a* (b* c) Commutative Property:& a* b = b * a Let's look at how the properties can help us understand the given exercise.
9 * -20
9 * (-1 * 20)
(-1 * 20) * 9
-1* (20* 9)
-1 * 180
- 180
When multiplying real numbers, the product will be positive if the signs are the same and it will be negative if the signs are different. cc Same Sign & Different Signs (+)(+)=(+) & (+)(-)=(-) (-)(-)=(+) & (-)(+)=(-)In our case both numbers are negative, so the product will be positive.
- 11 * - 16
11 * 16
176
We can verify this using a calculator.