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Simplify 32^(3/5)

Step by step, with the reason for every step · Rational exponents · Algebra 1

Step by step

The question

Question: work out 32^(3/5).

32^(3/5)

A fraction power has two jobs.

The bottom number, 5, says which root: the 5th root.

The top number, 3, says which power.

a^(m/n) = (n√a)m

Careful!

The power is not times.

32 times 3/5 is a different number.

Careful: not 32^(3/5) = 32 × 35 ✗

1 Take the root

The bottom is 5: the 5th root of 32.

The top is 3: to the power 3.

We take the root first.

It keeps the numbers small.

= (5√32)3

The 5th root of 32 is 2, because 2 × 2 × 2 × 2 × 2 is 32.

2 × 2 × 2 × 2 × 2 = 32

We write 2 in place of the 5th root of 32.

= 23

2 Take the power

2 to the power 3 is 2 × 2 × 2.

That is 8.

2 × 2 × 2 = 8

So 32^(3/5) = 8.

= 8

3 Check

Let's check the other way: the power first, then the root.

32 to the power 3 is 32768.

Other order: 323 = 32768

The 5th root of 32768 is 8, because 8 × 8 × 8 × 8 × 8 is 32768.

We get 8 again.

But the numbers were bigger.

So root first is easier.

And the answer is right!

5√32768 = 8, 8 × 8 × 8 × 8 × 8 = 32768

Let's look back.

First: take the root.

Then: take the power.

Last: check.

Answer
= 8

Your turn

Try this one yourself, then check:

Work out 64^(2/3)
Show the answer
16

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