# GRE Math : How to find patterns in exponents

## Example Questions

### Example Question #12 : Algebra

Quantitative Comparison

Quantity A: x2

Quantity B: x3

The two quantities are equal.

The relationship cannot be determined from the information given.

Quantity A is greater.

Quantity B is greater.

The relationship cannot be determined from the information given.

Explanation:

Let's pick numbers. For quantitative comparisons with exponents, it's good to try 0, a negative number, and a fraction.

0: 02 = 0, 03 = 0, so the two quantities are equal.

–1: (–1)2 = 1, (–1)3 = –1, so Quantity A is greater.

Already we have a contradiction so the answer cannot be determined.

### Example Question #1 : How To Find Patterns In Exponents

If , then which of the following must also be true?

Explanation:

We know that the expression must be negative. Therefore one or all of the terms x7, y8 and z10 must be negative; however, even powers always produce positive numbers, so y8 and z10 will both be positive. Odd powers can produce both negative and positive numbers, depending on whether the base term is negative or positive. In this case, x7 must be negative, so x must be negative. Thus, the answer is x < 0.

### Example Question #1 : How To Find Patterns In Exponents

Which quantity is the greatest?

Quantity A

Quantity B

The two quantities are equal.

The realationship cannot be determined from the information given.

Quantity A is greater.

Quantity B is greater.

Quantity A is greater.

Explanation:

First rewrite quantity B so that it has the same base as quantity A.

can be rewriten as , which is equivalent to .

Now we can compare the two quantities.

is greater than .

### Example Question #1 : How To Find Patterns In Exponents

Simplify the following:

Explanation:

With problems like this, it is always best to break apart your values into their prime factors. Let's look at the numerator and the denominator separately:

Numerator

Continuing the simplification:

Now, these factors have in common a . Factor this out:

Denominator

This is much simpler:

Cancel out the common factors of :

### Example Question #21 : Algebra

What digit appears in the units place when is multiplied out?

Explanation:

This problem is quite simple if you recall that the units place of powers of 2 follows a simple 4-step sequence.

Observe the first few powers of 2:

2= 2, 2= 4, 2= 8, 2= 16, 2= 32, 2= 64, 2= 128, 2= 256 . . .

The units place follows a sequence of 2, 4, 8, 6, 2, 4, 8, 6, etc. Thus, divide 102 by 4. This gives a remainder of 2.

The second number in the sequence is 4, so the answer is 4.

### Example Question #1 : How To Find Patterns In Exponents

Which of the following is a multiple of ?

Explanation:

For exponent problems like this, the easiest thing to do is to break down all the numbers that you have into their prime factors. Begin with the number given to you:

Now, in order for you to have a number that is a multiple of this, you will need to have at least  in the prime factorization of the given number.  For each of the answer choices, you have:

; This is the answer.

### Example Question #681 : Algebra

Simplify the following:

Explanation:

Because the numbers involved in your fraction are so large, you are going to need to do some careful manipulating to get your answer. (A basic calculator will not work for something like this.) These sorts of questions almost always work well when you isolate the large factors and notice patterns involved. Let's first focus on the numerator. Go ahead and break apart the  into its prime factors:

Note that these have a common factor of . Therefore, you can rewrite the numerator as:

Now, put this back into your fraction:
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