1. 4.4 Percent of Change Percent of change is the ratio When a value increases from its original amount, it is the percent of increase. When a value decreases from its original amount, it is the percent of decrease.

2. Finding Percent of Change The price of a sweater is decreased from $29.99 to $24.49. Find the percent of decrease. Percent of decrease = The price of the sweater decreased by about 18%.

3. Percent error Greatest possible error in a measuring unit is one half of that measuring unit. Example: –You use a beam balance to find the mass of a rock sample for a science lab. You read the scale as 3.8 g. What is your greatest possible error? –The rock’s mass is measured to the nearest 0.1 g, so the greatest possible erroris one half 0.1 g, or 0.05 g.

4. Finding Maximum and Minimum Areas You measure a room and make the diagram shown. Use the greatest possible error to find the maximum and minimum possible areas. 13 ft. 7 ft.

5. Both measures were made to the nearest whole foot, so the greatest possible error is 0.5 ft. The length could be as little as 12.5 ft, or as great as 13.5 ft. The width could be as little as 6.5 ft, or as great as 7.5 ft. Find the minimum and maximum areas. Minimum area 12.5 ft x 6.5 ft = 81.25 ft 2 Maximum area 13.5 ft x 7.5 ft = 101.25 ft 2

6. Percent Error Percent error is another useful way to think of the error in a measurement. It is the ratio of the greatest possible error and the measurement. Percent error = greatest possible error measurement

7. Finding Percent Error Suppose you measure a CD and record its diameter as 12.1 cm. Find the percent error in your measurement. Since the measurement is to the nearest 0.1 cm, the greatest possible error is 0.05 cm. So, the percent error is about 0.4%.

8. More Practice!!!! Homework - Textbook – p. 207 # 2 – 28 even, skip 14