Pre-Algebra Quiz: Exponent Rules

10 questions · exam conditions

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Exponent RulesQuestion 1 of 10

If $a^3 \cdot a^n = a^{11}$ and $\frac{a^{15}}{a^n} = a^7$ , what is the value of $n$ ?

Pre-Algebra Quiz

Pre-Algebra Quiz: Exponent Rules

Practice Exponent Rules in Pre-Algebra with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Exponent Rules, giving you a quick way to practice the rules, question types, and explanations that matter most for Pre-Algebra.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

If $a^3 \cdot a^n = a^{11}$ and $\frac{a^{15}}{a^n} = a^7$ , what is the value of $n$ ?

4
7
8 (correct answer)
11

Explanation: From the first equation:

a^3 \cdot a^n = a^{3+n} = a^{11}

, so

3 + n = 11

and

n = 8

. We can verify with the second equation:

\frac{a^{15}}{a^n} = a^{15-n} = a^7

, so

15 - n = 7

and

n = 8

. Both equations confirm

n = 8

. Choice A comes from solving only

n + 7 = 11

. Choice B comes from

15 - n = 8

. Choice D comes from misreading the first equation.

Question 2

Which of the following expressions equals $\frac{2^8}{2^3} \cdot \frac{2^6}{2^4}$ ?

$2^7$ (correct answer)
$2^{21}$
$\frac{2^{14}}{2^7}$
$\frac{2^{48}}{2^{144}}$

Explanation: Simplify each fraction separately:

\frac{2^8}{2^3} = 2^{8-3} = 2^5

and

\frac{2^6}{2^4} = 2^{6-4} = 2^2

. Then multiply:

2^5 \cdot 2^2 = 2^{5+2} = 2^7

. Choice B incorrectly adds all exponents (8+3+6+4). Choice C shows

\frac{2^{8+6}}{2^{3+4}}

but doesn't simplify further. Choice D incorrectly multiplies exponents.

Question 3

If $\frac{3^{2x}}{3^x} \cdot 3^{3x} = 3^{20}$ , what is the value of $x$ ?

4
5 (correct answer)
10
20

Explanation: First simplify the quotient:

\frac{3^{2x}}{3^x} = 3^{2x-x} = 3^x

. Then multiply:

3^x \cdot 3^{3x} = 3^{x+3x} = 3^{4x}

. Since

3^{4x} = 3^{20}

, we have

4x = 20

, so

x = 5

. Choice A comes from solving

5x = 20

. Choice C comes from solving

2x = 20

. Choice D gives the total exponent value instead of

x

Question 4

Simplify: $\frac{5^6 \cdot 5^2 \cdot 5^4}{5^3 \cdot 5^7}$

$5^2$ (correct answer)
$5^{22}$
$\frac{1}{5^2}$
$\frac{5^{12}}{5^{10}}$

Explanation: First simplify the numerator:

5^6 \cdot 5^2 \cdot 5^4 = 5^{6+2+4} = 5^{12}

. Then simplify the denominator:

5^3 \cdot 5^7 = 5^{3+7} = 5^{10}

. Finally apply the quotient rule:

\frac{5^{12}}{5^{10}} = 5^{12-10} = 5^2

. Choice B incorrectly adds all exponents. Choice C gives the reciprocal of the correct answer. Choice D shows an intermediate step but doesn't complete the simplification.

Question 5

If $2^x \cdot 2^{3x} = 2^{16}$ , what is the value of $x^2$ ?

4
8
16 (correct answer)
64

Explanation: Using the product rule for exponents,

2^x \cdot 2^{3x} = 2^{x+3x} = 2^{4x}

. Since

2^{4x} = 2^{16}

, we have

4x = 16

, so

x = 4

. Therefore,

x^2 = 4^2 = 16

. Choice A gives the value of

x

, not

x^2

. Choice B represents

2x

. Choice D represents

2^x

Question 6

Which expression is equivalent to $\frac{6^4 \cdot 6^7}{6^3 \cdot 6^2} \cdot \frac{6^5}{6^8}$ ?

$\frac{6^{16}}{6^{13}}$
$6^{11}$
$\frac{1}{6^3}$
$6^3$ (correct answer)

Explanation: When you encounter expressions with multiple exponents and the same base, you're working with the laws of exponents. The key is to systematically apply the rules for multiplying and dividing powers. Let's work through this step by step. First, simplify each fraction separately using the quotient rule: when dividing powers with the same base, subtract the exponents. For the first fraction:

\frac{6^4 \cdot 6^7}{6^3 \cdot 6^2}

In the numerator, use the product rule (add exponents):

6^4 \cdot 6^7 = 6^{4+7} = 6^{11}

In the denominator:

6^3 \cdot 6^2 = 6^{3+2} = 6^5

So the first fraction becomes:

\frac{6^{11}}{6^5} = 6^{11-5} = 6^6

The second fraction is already simplified:

\frac{6^5}{6^8} = 6^{5-8} = 6^{-3}

Now multiply these results:

6^6 \cdot 6^{-3} = 6^{6+(-3)} = 6^3

The answer is D. Let's examine why the other choices are wrong. Choice A (

\frac{6^{16}}{6^{13}}

) incorrectly adds all the exponents in numerators and denominators without proper grouping. Choice B (

6^{11}

) stops after simplifying only the first fraction. Choice C (

\frac{1}{6^3}

) makes a sign error, giving

6^{-3}

instead of

6^3

. Remember: work systematically through exponent problems by grouping terms properly and applying one rule at a time. Don't try to do everything at once, as this leads to errors in tracking positive and negative exponents.

Question 7

Which expression is equivalent to $\frac{3^8 \cdot 3^4}{3^5}$ ?

$3^7$ (correct answer)
$3^{17}$
$\frac{3^{12}}{3^5}$
$3^{32}$

Explanation: First apply the product rule:

3^8 \cdot 3^4 = 3^{8+4} = 3^{12}

. Then apply the quotient rule:

\frac{3^{12}}{3^5} = 3^{12-5} = 3^7

. Choice B incorrectly adds all exponents (8+4+5). Choice C shows the intermediate step but doesn't complete the simplification. Choice D incorrectly multiplies all exponents (8×4×5).

Question 8

If $7^m \cdot 7^{2m} \cdot 7^{3m} = 7^{18}$ , what is the value of $2m$ ?

3
6 (correct answer)
9
18

Explanation: Using the product rule:

7^m \cdot 7^{2m} \cdot 7^{3m} = 7^{m+2m+3m} = 7^{6m}

. Since

7^{6m} = 7^{18}

, we have

6m = 18

, so

m = 3

. Therefore,

2m = 2(3) = 6

. Choice A gives the value of

m

, not

2m

. Choice C gives the value of

3m

. Choice D gives the value of

6m

Question 9

If $\frac{x^9}{x^4} = x^a$ and $x^3 \cdot x^b = x^{11}$ , what is the value of $a + b$ ?

8
11
13 (correct answer)
14

Explanation: From the first equation:

\frac{x^9}{x^4} = x^{9-4} = x^5

, so

a = 5

. From the second equation:

x^3 \cdot x^b = x^{3+b} = x^{11}

, so

3 + b = 11

and

b = 8

. Therefore,

a + b = 5 + 8 = 13

. Choice A gives only the value of

b

. Choice B gives the exponent from the second equation. Choice D gives

a + 9

Question 10

Simplify: $\frac{4^5 \cdot 4^3}{4^6} \cdot 4^2$

$4^2$
$4^4$ (correct answer)
$4^{16}$
$\frac{4^8}{4^6}$

Explanation: First simplify the fraction:

\frac{4^5 \cdot 4^3}{4^6} = \frac{4^{5+3}}{4^6} = \frac{4^8}{4^6} = 4^{8-6} = 4^2

. Then multiply by

4^2

4^2 \cdot 4^2 = 4^{2+2} = 4^4

. Choice A stops after simplifying the fraction but doesn't multiply by

4^2

. Choice C incorrectly adds all exponents. Choice D shows an intermediate step without completing the calculation.