GRE Quant Essentials in 3 Minutes

Transcript

GRE Quantitative Reasoning rarely asks for advanced mathematics. It tests whether you can reason carefully with arithmetic, algebra and basic statistics, and whether you avoid the traps the test is built around. Let us cover the ideas that pay off most.

First, quantitative comparison. You are shown Quantity A and Quantity B and must decide the relationship. Choice A means Quantity A is always greater. Choice B means Quantity B is always greater. Choice C means the two are always equal. Choice D means the relationship cannot be determined from the information given. The key word is always. If you can find one case where A is bigger and another where B is bigger, the answer is D.

That is why you should plug in more than one kind of number. Suppose Quantity A is x squared and Quantity B is x. Try x equals two, and A is bigger. But try x equals one half, and x squared is one quarter, so B is bigger. Two different results means the answer is D. Always test zero, one, a negative number and a fraction, because those are the numbers that break patterns.

Second, percent change. The formula is the change divided by the original value, times one hundred. If a price rises from fifty to sixty, the change is ten, divided by the original fifty, which is twenty percent. Watch the trap: a twenty percent increase followed by a twenty percent decrease does not return you to the start. One hundred rises to one hundred twenty, then falls by twenty four to ninety six.

Third, think about averages as sums. The sum equals the average times the number of items. If four test scores average eighty, their total is three hundred twenty. If a fifth score brings the average to eighty two, the new total is four hundred ten, so the fifth score must be ninety. Working with sums is almost always faster than guessing.

Fourth, the basic exponent rules. When you multiply powers with the same base, add the exponents. When you divide, subtract them. When you raise a power to a power, multiply them. And any nonzero number to the power zero equals one.

Finally, estimate. Many answer choices are far apart, so rounding can confirm your answer or eliminate choices in seconds.

So here is your recap. In quantitative comparison, D means it depends, so test zero, negatives and fractions. Percent change divides by the original. Averages become sums. Know your exponent rules, and estimate whenever the choices allow it.