Big Ideas Math: Modeling Real Life, Grade 6
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Big Ideas Math: Modeling Real Life, Grade 6 View details
3. Solving Equations Using Multiplication or Division
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Exercise 32 Page 263

Use the Multiplicative Inverse Property to isolate c.

c=66

Practice makes perfect
To solve the equation, we have to isolate c on one side. Using the Multiplication Property of Equality, we will multiply both sides of the equation by the reciprocal of 215, which is 152. This will isolate c.
2c/15=8.8
15/2* 2c/15 =15/2* 8.8
15/2* 2/15* c =15/2* 8.8
1* c =15/2* 8.8
1* c =7.5* 8.8
c =66
To check that this solution is correct, let's substitute c=66 into the original equation and simplify.
2c/15=8.8
2( 66)/15? =8.8
132/15? =8.8
8.8=8.8 âś“
Since the left-hand side and right-hand side are equal, c=66 is the correct solution.

Extra

Properties of Equality

There are four main Properties of Equality that we use when solving linear equations.

Properties of Equality
Addition Property of Equality If a=b, then a+c=b+c.
Subtraction Property of Equality If a=b, then a-c=b-c.
Multiplication Property of Equality If a=b, then ac=bc.
Division Property of Equality If a=b and c is not 0, then a/c=b/c.

In later chapters, you will learn about some more advanced Properties of Equality. As an example, there is a property for when we need to eliminate a radical or an exponent.

Power Property of Equality

If a=b, then a^m=b^m.