GMAT quant silly mistakes

Hi Ananyaroy27,

There are a multitude of possible reasons why you are making careless errors, from not reading carefully to writing sloppily to making mental math mistakes. It’s also entirely possible that your careless errors are due, in some part, to a relative lack of GMAT quant knowledge in certain areas. You’ve already mentioned Geometry and Inequalities, but I’d bet there are even more! After all, on any GMAT, you must answer difficult and convoluted math questions in a timed and pressure-filled environment, so if you don’t know GMAT quant like the back of your hand, careless errors are likely, right? Take the following example:

14! is equal to which of the following?

(A) 87,178,291,200
(B) 88,180,293,207
(C) 89,181,294,209
(D) 90,000,000,003
(E) 91,114,114,114

Upon seeing this question, what is the first thing that comes to mind? Grabbing a calculator to add up the values in the expression? If you are able to quickly recognize that using the “5 x 2 pair rule” will allow you to efficiently attack the problem (see the solution below), the question becomes very basic, and you can avoid having to perform tedious calculations that are likely to result in a silly mistake.

Solution:

Notice that there is at least one (5 × 2) pair contained in the product of these numbers. It follows that the units digit must be a zero. The only number with zero as the units digit is 87,178,291,200.

Answer: A

This is just one example, but hopefully you can see that by a) recognizing what the question is asking and b) properly attacking the question, your propensity to make a silly mistake greatly decreases.

You may find it helpful to read about all of this in further detail in my article about improving your accuracy on the GMAT.

Feel free to reach out with further questions.

Good luck!