# Exponents and Division – the Quotient of Powers Property04:09 minutes

Video Transcript

## TranscriptExponents and Division – the Quotient of Powers Property

In the year 8008, data is the new money. The more you have, the more you control. We’re at the Schmoogle Headquarters at the lead data trader’s desk, model number AA-RN0, but everyone calls him Arn0. He seems really busy at his job as a data trader. Let’s take a closer look at what he’s working on. He's talking to his head of engineering, Smicha, who needs to calculate the number of hard drives he needs in order to store all the data on the internet. AA-RN0 is making plans to backup the entire Internet, which is 10²⁵ brontobytes, to become the richest robot in the universe.
But Smicha only has 10¹⁵ brontobytes of space on each of his hard drives. AA-RN0 has a problem. His calculator doesn’t show enough digits for an accurate calculation. Not knowing what to do, AA-RN0 asks Smicha if he has any ideas. Smicha knows a method to deal with really large numbers and thinks that his knowledge of dividing exponents might come in handy.

### Division of Exponents

Smicha shows AA-RN0 that aᵐ / aⁿ = a⁽ᵐ⁻ⁿ⁾, but he warns AA-RN0 that the bases of both numbers have to be the same. Smicha shows AA-RN0 a quick example with numbers instead of letters to help him understand Exponents and Division.
2⁵ / 2³ = 2⁽⁵⁻³⁾ = 2². As you know, this is the same as 32 / 8, which is 4, the same answer we just got. AA-RN0 gives the calculation another try. If the internet has 10²⁵ brontobytes of space, and each of their Gen1 hard drives can hold 10¹⁵ brontobytes of space, AA-RN0 notices that his base is 10, so he writes that down. He then writes 10²⁵ / 10¹⁵ and knows that this equals 10⁽²⁵⁻¹⁵⁾ which is the same as 10¹⁰. Smicha tells AA-RN0 that they need 10¹⁰ hard drives to store all the data.
TEN BILLION ROBOTS!?!? THEY'LL NEVER FINISH!!!

Good news! Smicha just received the Beta model for the Gen2 hard drive. The new Gen2 hard drives can each hold 10¹⁸ brontobytes of data. Smicha now needs to know how many Gen2 hard drives he’ll need to store all the internet’s data. He writes 10²⁵ / 10¹⁸. Following the steps Smicha outlined for him earlier, AA-RN0 rewrites the division expression as 10⁽²⁵⁻¹⁸⁾, which gives him 10⁷ hard drives. They only need to produce 10 million hard drives! They'll be done in a jiffy!

### Summary

In order to remember the steps for Exponents and Division, Smicha saves the equation in his memory. aᵐ / aⁿ = a⁽ᵐ⁻ⁿ⁾
When dividing exponents, if the bases are the same, you can simply subtract the exponents from the numerator and the denominator.

Smicha now has to make sure all the robots are built on time what’s this? I guess the future's not so different after all...

1 comment
1. Very cool! And informative!

Posted by Plano Kellmeyer, almost 4 years ago

## Exponents and Division – the Quotient of Powers Property Exercise

### Would you like to practice what you’ve just learned? Practice problems for this video Exponents and Division – the Quotient of Powers Property help you practice and recap your knowledge.

• #### Explain how to divide $2^5$ by $2^3$.

##### Hints

Remember that $2^5=2\times 2\times 2\times 2\times 2$.

We can see that $2\times 2\times 2$ in the denominator of $\frac{2\times 2\times 2\times 2 \times 2}{2\times 2 \times 2}$ can cancel out three of the $2$'s in the numerator.

##### Solution

The quotient of powers property says that dividing two powers with the same base is the same as subtracting the exponent of the denominator from the exponent of the numerator and raising the base to that power.

Generally, this can be stated as $\frac{a^m}{a^n}=a^{(m-n)}$.

$~$

Using the quotient of powers property with our example, we have:

$\frac{2^{\large 5}}{2^{\large 3}}=2^{(5-3)}=2^2$.

$~$

Looking at our example even more explicitly, we have that

${\large\frac{2^5}{2^3}}=\frac{2\times 2\times 2\times 2 \times 2}{2\times 2 \times 2}$.

Because we have the factor $2$ five times in the numerator and three times in the denominator we can cancel out three $2$'s in the denominator with three $2$'s in the numerator, giving us

$\frac{2\times 2\times 2\times 2 \times 2}{2\times 2 \times 2}=2^2$.

$~$

We can also come to the same conclusion by dividing $2^5=32$ by $2^3=8$:

$\frac{32}8=4=2^2$.

• #### Determine the number of hard drives AA-RNO needs to store an entire copy of the internet.

##### Hints

Keep the quotient of powers property in mind: subtract the exponents and raise the base to this power.

Here is an example:

Remember to subtract the exponent of the denominator from the exponent of the numerator... the order matters here!

##### Solution

the quotient of powers property says that we should subtract the exponents and raise the common base to the result: $\frac{a^m}{a^n}=a^{(m-n)}$

$~$

So, if we have to divide the total brontobytes we need, $10^{25}$, by any decimal power with base 10, we only have to subtract the exponents and raise 10 to the resulting power.

$~$

For our hard drive options, we have:

$\frac{10^{\large 25}}{10^{\large 15}}=10^{(25-15)}=10^{10}$

and as well

${\large\frac{10^{25}}{10^{18}}}=10^{(25-18)}=10^{7}$

$~$

Pay attention to the order of subtraction: You have to subtract the exponent of the denominator from the exponent of the numerator, and not the other way around!

• #### Decide which division the quotient of powers property can be used.

##### Hints

This power has basis $a$ and exponent $m$.

Keep in mind that the basis must match... not the exponents.

##### Solution

We can apply the quotient of powers property to powers which have the same base. Then we only have to subtract the exponent of the denominator from the exponent of the numerator and raise the base to the result:

• ${\large\frac{10^{22}}{10^2}}=10^{(22-2)}=10^{20}$
• ${\large\frac{10^{22}}{10^{12}}}=10^{(22-12)}=10^{10}$
• ${\large\frac{10^{22}}{10^3}}=10^{(22-3)}=10^{19}$
• ${\large\frac{3^{17}}{3^5}}=3^{(17-5)}=3^{12}$
• ${\large\frac{3^{17}}{3^{10}}}=3^{(17-10)}=3^{7}$
• ${\large\frac{5^{19}}{5^{10}}}=5^{(19-10)}=5^{9}$
• ${\large\frac{5^{19}}{5^{3}}}=5^{(19-3)}=5^{16}$
• ${\large\frac{5^{19}}{5^{12}}}=5^{(19-12)}=5^{7}$
• #### Examine the growth of the internet data volume between 3008 and 8008.

##### Hints

If you have powers with the same basis you can apply the quotient of powers property:

Subtract the exponent of the denominator from the exponent of the numerator, not the other way round.

Let's have a look at an example:

##### Solution

To get the growth $g$ of the internet volume between 8008 and 3008, we have to solve the equation

$g\times 10^{12}=10^{25}$.

To get the factor $g$, we need to divide by $10^{12}$; so we have

$g={\large\frac{10^{25}}{10^{12}}}$.

Since we have two powers with the same basis, we can apply the quotient of powers property and subtract the exponents in the following way:

$g=10^{(25-12)}=10^{13}$.

Thus we can see that the internet data volume has grown by the factor of $10^{13}$.

Indeed, that is amazing growth!

• #### Describe the quotient of powers property.

##### Hints

Remember that $a^n=\underbrace{a\times ...\times a}_{\text{n times}}$

In this example, we can see that the two $3$'s in the denominator cancel out with two of the $3$'s in the numerator.

In this example, nothing in the denominator can cancel out with anything in the numerator.

##### Solution

This is the formula for the quotient of powers property.

Let's talk about what it means. This property assists with simplifying powers, but only if they have the same basis.

When dividing powers with the same basis, you can simply subtract the exponent of the denominator from the exponent of the numerator and raise the common basis to the result.

• #### Carry out the following divisions.

##### Hints

Keep the common basis and subtract the exponents.

Pay attention to the order of subtraction. If you change the order of subtraction you'll get a negative exponent. This is also possible but wrong, for instance, for the following example:

The resulting exponent can also be zero.

$a^0=1$, as long as $a\neq 0$.

##### Solution

If you have to divide two powers with the same basis, you only have to subtract the exponents in the right order: subtract the exponent of the denominator from the exponent of the numerator. The basis of the result stays the same.

• ${\large\frac{9^{12}}{9^{11}}}=9^{(12-11)}=9^1=9$
• ${\large\frac{3^{35}}{3^{33}}}=3^{(35-33)}=3^2=9$
• ${\large\frac{5^{5}}{5^{2}}}=5^{(5-2)}=5^3=125$
• ${\large\frac{4^{8}}{4^{8}}=4^{(8-8)}}=4^0=1$
• ${\large\frac{6^{13}}{6^{10}}}=6^{(13-10)}=6^3=216$
• ${\large\frac{7^{43}}{7^{21}}}=7^{(43-21)}=7^{22}$