Target Test Prep Representative
Joined: 12 Sep 2018
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Re: should I use calculator or not?
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25 Jul 2019, 07:38
Using the calculator when solving quant problems on the GRE is not necessarily a bad thing. However, you just want to make sure that you are always being efficient, right? In other words, you don’t want to be so reliant on using the calculator that you use it for situations in which you’d be better off relying on a math rule. For example, take a look at the following problem:
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 using the GRE calculator.
Solution:
14! = 14 × 13 × 12 × 11 × 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1.
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
Although this is just one example of many, you see that you must have many tools in your toolbox to efficiently attack each GRE quant question that comes your way. As you learn new quant skills, you will be able to make an informed decision about when to use the GRE calculator.
Feel free to reach out with further questions.
Good luck!