5.4 Solving Proportions - McGraw Hill Education（5.4解决比例麦格劳希尔教育）.pdf

5.4 Solving Proportions 5.4 OBJECTIVE 1. Solve a proportion for an unknown value A proportion consists of four values. If three of the four values of a proportion are known, you can always find the missing or unknown value. a 10 In the proportion , the first value is unknown. We have chosen to represent the 3 15 unknown value with the letter a. Using the proportion rule, we can proceed as follows. ? 10 a 10 NOTE is a proportion 3 15 3 15 in which the first value is unknown. Our work in this 15 a 3 10 or 15 a 30 section will be learning how to find that unknown value. The equals sign tells us that 15 a and 30 are just different names for the same number. This type of statement is called an equation. Definitions: Equation An equation is a statement that two expressions are equal. One important property of an equation is that we can divide both sides by the same nonzero number. Here let ’s divide by 15. 15 a 30