GMAT Question of the Day - Data Sufficiency - Algebra/Percent Change
What was the percent change in total sales for Company G from 1995 to 1999?
1) The total sales for Company G in 1999 were $5760 less sales than total sales for Company G in 1995.
2) In 1997 total sales were 12% greater than they were 1995, and in 1999 total sales were 12% lower than they were in 1997
GMAT Question of the Day Solution
The question is: can you create a relationship between the sales in 1995 and the sales in 1999? Note that for this question (and any other questions that deal with relative change) you do not need to know the exact numbers.
1) This statement only tells you the difference in sales between 1995 and 1999 but not the total sales in each year. Depending on the total sales the percent change will be different. This doesn't give you a proportional relationship (what you would need to determine the percent change). If you change the numbers around you will get different values for the percent change. Try making the 1995 total sales equal to zero and then try making them equal to 1,000,000. You will get vastly different values for the percent change (the $5760 could be a big change or a little one depending on the underlying sales). One of the things that GMAT students have trouble with is picking values. In GMAT tutoring sessions I often hear horror stories of DS questions that took 10 minutes because of all of the different values that the student had tried. Well, in general when picking values think in terms of the extremes. Try the minimum possible value. Try the maximum possible value. Do this within reason. Here we could have tried positive infinity but it's just more practical to pick 1,000,000.
2) Statement two is more interesting in that it creates a relationship among the sales for 1995, 1997, and 1999. You could set up a relationship between 1995 and 1999 and so solve for the percent change. Sufficient.