2 10 Change Expressed as a Percent I

2. 10 Change Expressed as a Percent I can find percent change and find the relative error in linear and nonlinear measurements.

Percent Change �Expresses an amount of change as a percent of an original amount. �If a new amount is greater, the change is a percent increase. �If a new amount is less, it is a percent decrease. �Ratio of the amount of change to the original amount

Finding a Percent Change �

You Try! �A store buys an electric guitar for $295 and marks up the price to $340. What is the markup expressed as a percent change? �≈15%

Relative Error �Ratio of the absolute value of the difference of a measured (or estimated) value and an actual value compared to the actual value. �When expressed as a percent, it is called percent error.

Practice �A decorator estimates that a rectangular rug is 5 ft by 8 ft, but it is actually 4 ft by 8 ft. Find the percent error. � 25%

Minimum and Maximum Dimensions �Often, actual measurements are not known. �You cannot always be completely accurate. �Think about measuring with a ruler. Precision is limited and sometimes you have to round. �The most any measurement can be off is by half of the unit used to measure.

Example �You measure the length of a poster to be 18. 5 in to the nearest half inch. What are the minimum and maximum possible lengths of the poster? �You measured to the nearest half inch, so the greatest possible error is 0. 25 in (half of your units) in either direction.

Greatest Possible Percent Error �The dimensions of a gift box are shown to the nearest inch. What is the greatest possible percent error in calculating the box’s volume? �What do we know? �Greatest possible error is 0. 5 in �V = lwh �What are we looking for? �Solve

Continued �

Assignment �ODDS ONLY �P. 148 #7 -23