Data Sufficiency questions are always the trickiest of the Math questions on the GMAT. But it may be interesting to know that in order to solve many of the Data Sufficiency questions on the GMAT you may not really need to do any Math.
As we say at Manya- The Princeton Review, the task is to evaluate, not to calculate!
OG 2017 Q. No. 258
In each of the last five years, company K donated p percent of its annual profits to a certain scholarship fund. Did company K donate more than $10,000 to the scholarship fund last year?
(1) Two years ago, Company K had annual profits of $3 million and donated $15,000 to the scholarship fund.
(2) Last year, Company K had annual profits of $2.5 million.
In this question we need to check whether the amount donated last year is greater than $10,000 or not. To find the donated amount we need the value of ‘p‘ and the annual profits last year.
From statement (1) we can find out the value of ‘p‘ but not the annual profits last year whereas from statement (2) we can find the annual profits last year but not the value of ‘p‘. When we combine both the statements we have both the value of ‘p‘ and the profits last year. Hence, we can find out the amount donated last year.
However, there is no need to calculate the amount donated. We know that it can be calculated; it will be either more than $10,000 or not. We are not concerned! The answer is C.
And now, here comes the most beautiful of such questions on OG 2017.
OG 2017 Q. No. 262
In cross section, a tunnel that carries one lane of one-way traffic is a semicircle with radius 4.2m. Is the tunnel large enough to accommodate truck that is approaching the entrance to the tunnel?
(1) The maximum width of the truck is 2.4 m.
(2) The maximum height of the truck is 4 m.
In this question we need to check whether truck can fit inside the tunnel or not. For this we need the dimensions of the truck as we already know the dimensions of the tunnel. But what dimensions? The
Statement (1) gives me the width of the truck but not the height. Statement (2) gives me the height of the truck but not the width. When we combine the statements we get both the height and the width. Therefore, both statements together are sufficient to answer the question. The answer is C
You really do not need to find out whether the tunnel is large enough to accommodate the truck. There is no need to calculate. It’s enough to know that it can be worked out whether the tunnel is large enough to accommodate the truck or not! The truck will pass or not pass. That’s it. The answer is C.
Did we really need to do any math to answer any of the above two questions? No.
GMAC rightly says that the “Quantitative section measures your ability to analyze data and draw conclusions using reasoning skills” – not your ability to calculate. This is all the more true in respect of Data Sufficiency questions. Problem solving questions may, however, be a different ball game.