For Choice A, since the only data given in Figure 8 are percent changes from year to year, there is no way to compare the actual dollar amount of sales at the stores for 2008 or for any other year. Even though Store R had the greatest percent increase from 2006 to 2008, its actual dollar amount of sales for 2008 may have been much smaller than that for any of the other four stores, and therefore Choice A is not necessarily true. For Choice B, even though the sum of the two percent decreases would suggest a 22 percent decrease, the bases of the percents are different. If B is the dollar amount of sales at Store S for 2006, then the dollar amount for 2007 is 93 percent of B, or and the dollar amount for 2008 is given by 0.93B, (0.85)(0.93)B, which is Note that this represents a percent decrease of 0.7905B. percent, which is less than 22 percent, and so Choice B is 100 − 79.05 = 20.95 not true.
For Choice C, if C is the dollar amount of sales at Store R for 2006, then the dollar amount for 2007 is given by and the dollar amount for 2008 is given 1.05C by which is Note that this represents a 17.6 percent (1.12)(1.05)C, 1.176C. the increase, which is greater than 17 percent, so Choice C must be true.