PSAT Math : How to find patterns in exponents

Study concepts, example questions & explanations for PSAT Math

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Example Questions

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Example Question #1 :How To Find Patterns In Exponents

If ax·a4= a12and (by)3= b15, what is the value of x - y?

Possible Answers:

-9

-2

3

-4

6

有限公司rrect answer:

3

Explanation:

Multiplying like bases means add the exponents, so x+4 = 12, or x = 8.

Raising a power to a power means multiply the exponents, so 3y = 15, or y = 5.

x - y = 8 - 5 = 3.

Example Question #1 :Pattern Behaviors In Exponents

If p and q are positive integrers and 27p= 9q, then what is the value of q in terms of p?

Possible Answers:

p

(3/2)p

3p

2p

(2/3)p

有限公司rrect answer:

(3/2)p

Explanation:

The first step is to express both sides of the equation with equal bases, in this case 3. The equation becomes 33p= 32q. So then 3p = 2q, and q = (3/2)p is our answer.

Example Question #1 :How To Find Patterns In Exponents

Simplify 272/3.

Possible Answers:

3

27

9

125

729

有限公司rrect answer:

9

Explanation:

272/3is 27 squared and cube-rooted. We want to pick the easier operation first. Here that is the cube root. To see that, try both operations.

272/3= (272)1/3= 7291/3OR

272/3= (271/3)2= 32

Obviously 32is much easier. Either 32or 7291/3will give us the correct answer of 9, but with 32it is readily apparent.

Example Question #4 :Pattern Behaviors In Exponents

Ifandare integers and

what is the value of?

Possible Answers:

有限公司rrect answer:

Explanation:

To solve this problem, we will have to take the log of both sides to bring down our exponents. By doing this, we will get\dpi{100} \small a\ast log\left (\frac{1}{3} \right )= b\ast log\left ( 27 \right ).

To solve for\dpi{100} \small \frac{a}{b}we will have to divide both sides of our equation by\dpi{100} \small log\frac{1}{3}to get\dpi{100} \small \frac{a}{b}=\frac{log\left ( 27 \right )}{log\left ( \frac{1}{3} \right )}.

\dpi{100} \small \frac{log\left ( 27 \right )}{log\left ( \frac{1}{3} \right )}will give you the answer of –3.

Example Question #5 :Pattern Behaviors In Exponents

Ifand, then what is?

Possible Answers:

有限公司rrect answer:

Explanation:

We use two properties of logarithms:

log(xy) = log (x) + log (y)

log(x^{n}) = nlog (x)

So

Example Question #6 :Pattern Behaviors In Exponents

Evaluate:

x^{-3}x^{6}

Possible Answers:

x^{9}

x^{6}

x^{-3}

x^{-18}

x^{3}

有限公司rrect answer:

x^{3}

Explanation:

x^{m}\ast x^{n} = x^{m + n}, hereand, hence.

Example Question #2 :How To Find Patterns In Exponents

Solve for

\left ( \frac{2}{3} \right )^{x+1} = \frac{27}{8}

Possible Answers:

None of the above

有限公司rrect answer:

Explanation:

\left ( \frac{2}{3} \right )^{x+1} = \frac{27}{8}=\left ( \frac{3}{2} \right )^{3} = \left ( \frac{2}{3} \right )^{-3}

which means

Example Question #12 :Pattern Behaviors In Exponents

Which of the following statements is the same as:

Possible Answers:

有限公司rrect answer:

Explanation:

Remember the laws of exponents. In particular, when the base is nonzero:

An effective way to compare these statements, is to convert them all into exponents with base 2. The original statement becomes:

This is identical to statement I. Now consider statement II:

Therefore, statement II is not identical to the original statement. Finally, consider statement III:

which is also identical to the original statement. As a result, only I and III are the same as the original statement.

Example Question #13 :Pattern Behaviors In Exponents

Write in exponential form:

Possible Answers:

有限公司rrect answer:

Explanation:

Using properties of radicals e.g.,

we get

Example Question #261 :Exponents

Write in exponential form:

Possible Answers:

有限公司rrect answer:

Explanation:

Properties of Radicals

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