Exercise 18 Page 415

To determine percent change p, we can use the following general formula. p % =Amount of increase or decrease/Original amountFrom the given values, we can see the original amount was $15 and the new amount is $20. This is an increase in the amount. 20-15= 5 The difference between the new amount and the original amount is $5. Now we can use the formula.

Percent change=Amount of increase/Original amount

SubstituteValues

Substitute values

Percent change=5/15

ReduceFrac

a/b=.a /5./.b /5.

Percent change=1/3

UseCalc

Use a calculator

Percent change=0.33

WritePercent

Convert to percent

Percent change = 33 %

The percent increase is 33 %.