 Finding the Missing Exponent (Power) Revision | KS3 Maths Resources

## What you need to know

Things to remember:

• An exponent, or power, tells us how many times we multiply a number by itself.

What is the value of $x$ if $3^x=81$?

Remember, an exponent is telling us that we multiply a number by itself a certain number of times. So, this question is asking us to see how many times we have to multiply 3 by itself to make 81. The easiest way to this is to just build it up.

$x=1$ $3^1=3$

$x=2$ $3^2=3\times3=9$

$x=3$ $3^3=3\times3\times3=9\times3=27$

$x=4$ $3^4=3\times3\times3\times3=9\times3\times=27\times3=81$

So, we can see that $x=4$!

$$3^4=81$$

## Example Questions

$x=1$ $4^1=4$

$x=2$ $4^2=4\times4=16$

So, we can see that $x=4$!

$$4^2=16$$

$x=1$ $5^1=4$

$x=2$ $5^2=5\times5=25$

$x=3$ $5^3=5\times5\times5=25\times5=125$

$x=4$$5^4=5\times5\times5\times5=25\times5\times5=125\times5=625$

So, we can see that $x=4$!

$$5^4=625$$

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