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Write 0.0555... as a fraction

Step by step, with the reason for every step · Repeating decimals to fractions · Foundations

Step by step

The question

Question: write 0.0555 repeating as a fraction.

0.0555…

Look at the digits.

0 comes once.

Then 5 repeats for ever.

0 once, then 5 for ever

1 Call it x

We do not know the fraction yet.

So we call the number x: x = 0.0555 repeating.

x = 0.0555…

Careful!

It is not 5/100.

That is 0.05, which stops.

Ours goes on for ever.

Careful: not 0.0555… = 5100 ✗

2 Move the point

First we move the point past the 0, which does not repeat.

Times 10 moves the point 1 place to the right.

We do it to both sides, so they stay equal.

10x = 0.555…
× 10: point moves 1 place

Then one block more: times 100 moves it 2 places.

Now both numbers have the same tail after the point.

100x = 5.555…
× 100: point moves 2 places

3 Take away

Now we take the smaller one away from the bigger one.

Both sides, so they stay equal.

100x − 10x = 5.555… − 0.555…

After the point, both go on with 5 for ever.

The tails are exactly the same, so they make zero.

Cross them out.

100x minus 10x is 90x.

5 minus 0 is 5.

90x = 5

4 Remove the 90

90x means 90 times x.

We want just x.

To remove times 90, we divide by 90.

90x90 = 590

90 divided by 90 is 1.

So just x is left.

5 and 90 can both be divided by 5.

We can make 5/90 simpler.

It is the same as 1/18.

5 ÷ 590 ÷ 5 = 118

So x = 1/18.

x = 118

So 0.0555 repeating is 1/18.

5 Check

Let's check: 1 divided by 18.

We get 0.0555, and the digits go on the same way.

That is 0.0555 repeating.

So the answer is right!

1 ÷ 18 = 0.0555…

Let's look back.

First: call it x.

Then: move the point.

Then: take away.

Then: remove the 90.

Last: check.

Answer
x = 118

Your turn

Try this one yourself, then check:

Write 0.5666…
Show the answer
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