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You have 75 minutes to answer 37 questions. This means that you have about 2 minutes to answer each question and you can't use a calculator. In addition, the dry erase paper isn't suited to writing out complex calculations. As a result, you simply don't have the time or the means to do highly tedious calculations, so they must be avoided.
Keep in mind that the GMAT is a test of intelligence, not an attempt to determine if you are a human calculator. So the GMAT doesn't want you to waste 10 minutes doing calculations. The GMAT is more concerned with your ability to find tricks and shortcuts. The result of these factors is that questions will almost always have shortcuts (visible only to the brightest students) designed so that the question can be answered in a fraction of the time.
What is the sum of numbers from 1 to 100, inclusive?
Please do not start adding those numbers on test day. Don't get stuck in Plow mode and waste enormous amounts of time doing calculations. If you are taking 5 minutes, or the question looks as if it will take 5 minutes..... HALT! There's a nasty GMAT TRAP you've just stepped into. Take a second.... inhale .....exhale and then defuse the trap. Somewhere in that question there must be a shortcut! (As an aside, in a later chapter we will teach you a shortcut to add the numbers from 1 to 100 in just a few seconds).
If you must do intense calculations, these shortcuts will make it much easier.
a) Divide and compare fractions through estimating
What is 36,568/12,985?
a) 4.234
b) 2.816
c) 5.65
Instead of actually dividing those two numbers, just look at it and do you see the numbers look like 36/12 or 3?
Next, look down at the answer choices. Do you see something near 3? If you do, then you just found the shortcut.
The answer is 2.816 (choice B) and it took 3 seconds for you to do this shortcut instead of 30 seconds to divide 36,568/12,985. Congratulations, you just saved 27 seconds!
It helps when dealing with fractions to simplify it to resemble an integer or a basic fraction like 1/4, 1/2 and 3/4.
Use this technique to compare and comprehend fractions quickly.
Which is greater:
24/51 or 26/49?
24 is less than half of 50, so it is below 1/2. 26 is greater than half of 50, so 26/49 is larger than 24/51.
b) Multiply the last digits
If the final step of your calculation is
123 × 341 = ?
Simply take a look at the answer choices. Multiply the last digit by the last digit. You get 123 x 341 or 3
The GMAT is a multiple choice test. Pick the answer choice ending in 3.
c) Always look to cancel
3 × 324
162 × 4
Can be easily solved by canceling the 162 into 324 to get the final answer of 3/2. The GMAT often provides these easy cancellation shortcuts to save you time. It goes without saying that the GMAT will often make you have to factor or be very sharp to see how numbers can quickly cancel out.
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