3-7: Percent of Change

3-7: Percent of Change Percent of change When a value increases from its original amount, it is a percent increase. When a value decreases, it is a percent decrease.

3-7: Percent of Change Example 1 The price of a sweater decreased from $29.99 to $24.49. Find the percent decrease. The price decreased by about 18%

3-7: Percent of Change Your Turn Find the percent of change if the price of a t-shirt increases from $12.99 to $13.99. Round to the nearest percent. 8% Find the percent of change if that shirt goes on sale, and its price decreases from $13.99 to $12.99. Round to the nearest percent. 7%

3-7: Percent of Change Example 2 In 1990, there were 1330 registered alpacas in the United States. By the summer of 2000, there were 29,856. What was the percent of increase of registered alpacas? An increase of 2145%

3-7: Percent of Change Your Turn The number of alpaca owners increased from 146 in 1991 to 2919 in 2000. Find the percent of increase. Round to the nearest percent. 1899%

3-7: Percent of Change The greatest possible error in a measurement is one half the smallest measured unit. Example 3 You use a beam balance to find the mass of a rock sample. You read the scale as 3.8 g. What is your greatest possible error? The smallest measured unit is 0.1 g, so the greatest possible error is half that, 0.05 g

3-7: Percent of Change Your Turn You measure a picture for the yearbook and record its height at 9 cm. What is your greatest possible error? 0.5 cm

3-7: Percent of Change Example 4 You measure a room and find that it is 13 ft by 7 ft. Use the greatest possible error to find the maximum and minimum possible areas. Because each is measured to the nearest foot, the greatest possible error is 0.5 ft. That means the biggest the walls could be are 13.5 ft by 7.5 ft. 13.5 ● 7.5 = 101.25 ft2 The smallest the walls could be are 12.5 ft by 6.5 ft 12.5 ● 6.5 = 81.25 ft2

3-7: Percent of Change Your Turn You measure a wall of your room as 8 ft by 12 ft. Find the minimum and maximum possible areas of the wall. Minimum: 86.25 ft2 Maximum: 106.25 ft2

3-7: Percent of Change Percent error Example 5 Your Turn Find the greatest possible error for a measurement of 14 ft Greatest possible error: 0.5 ft Percent error: 0.5/14 ≈ 0.0357 = 3.6% Your Turn Find the percent error for a measurement of 2 cm 25%

3-7: Percent of Change Assignment Worksheet #3-7 1 – 39, odd problems