Simplify the Expression: 81 Divided by 3²

Exponent Division with Base Recognition

8132= \frac{81}{3^2}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:03 Let's solve this problem together.
00:06 We'll use the formula for dividing powers with the same base.
00:10 Remember: The base stays the same, and we subtract the exponents.
00:15 Now, let's apply this formula to our problem.
00:19 We'll express the number as a power of 3.
00:24 Then, subtract the exponent in the numerator from the exponent in the denominator.
00:30 And that's the solution! Great job!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

8132= \frac{81}{3^2}=

2

Step-by-step solution

First, we recognize that 81 is a power of the number 3, which means that:

34=81 3^4=81 We replace in the problem:

8132=3432 \frac{81}{3^2}=\frac{3^4}{3^2} Keep in mind that the numerator and denominator of the fraction have terms with the same base, therefore we use the property of powers to divide between terms with the same base:

bmbn=bmn \frac{b^m}{b^n}=b^{m-n} We apply it in the problem:

3432=342=32 \frac{3^4}{3^2}=3^{4-2}=3^2 Therefore, the correct answer is option b.

3

Final Answer

32 3^2

Key Points to Remember

Essential concepts to master this topic
  • Recognition: Identify that 81 is 34 3^4 before dividing
  • Division Rule: Use bmbn=bmn \frac{b^m}{b^n} = b^{m-n} when bases match
  • Check: Verify 32=9 3^2 = 9 and 819=9 \frac{81}{9} = 9

Common Mistakes

Avoid these frequent errors
  • Dividing 81 ÷ 9 directly without recognizing exponent patterns
    Don't calculate 81 ÷ 9 = 9 and write 9 as the final answer! This misses the exponent pattern and gives a numerical result instead of the required exponential form. Always express 81 as 34 3^4 first, then apply the division rule for exponents.

Practice Quiz

Test your knowledge with interactive questions

\( (2^3)^6 = \)

FAQ

Everything you need to know about this question

How do I know that 81 equals 3 to some power?

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Look for patterns! Start with small powers: 31=3 3^1 = 3 , 32=9 3^2 = 9 , 33=27 3^3 = 27 , 34=81 3^4 = 81 . Practice recognizing common powers to make these problems faster!

Can I just calculate 81 ÷ 9 = 9 and be done?

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While 81÷9=9 81 ÷ 9 = 9 is correct numerically, the question asks for an exponential form. Since 9=32 9 = 3^2 , the answer must be 32 3^2 , not just 9.

What if the numbers don't have the same base?

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If you can't express both terms with the same base, then you cannot use the exponent division rule. You'd need to calculate the actual values and divide normally.

Why is the exponent rule so important here?

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The exponent division rule bmbn=bmn \frac{b^m}{b^n} = b^{m-n} keeps your answer in exponential form, which is often required. Plus, it's much faster than calculating large numbers!

How do I remember the subtraction rule for dividing exponents?

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Think: "When dividing, subtract the powers!" 3432 \frac{3^4}{3^2} means you have 4 threes multiplied, then you're dividing by 2 threes, leaving you with 42=2 4 - 2 = 2 threes.

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