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Write 1.1666... as a fraction

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

Step by step

The question

Question: write 1.1666 repeating as a fraction.

1.1666…

Look at the digits.

1 comes once.

Then 6 repeats for ever.

1 once, then 6 for ever

1 Call it x

We do not know the fraction yet.

So we call the number x: x = 1.1666 repeating.

x = 1.1666…

Careful!

It is not 116/100.

That is 1.16, which stops.

Ours goes on for ever.

Careful: not 1.1666… = 116100 ✗

2 Move the point

First we move the point past the 1, 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 = 11.666…
× 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 = 116.666…
× 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 = 116.666… − 11.666…

After the point, both go on with 6 for ever.

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

Cross them out.

100x minus 10x is 90x.

116 minus 11 is 105.

90x = 105

4 Remove the 90

90x means 90 times x.

We want just x.

To remove times 90, we divide by 90.

90x90 = 10590

90 divided by 90 is 1.

So just x is left.

105 and 90 can both be divided by 15.

We can make 105/90 simpler.

It is the same as 7/6.

105 ÷ 1590 ÷ 15 = 76

So x = 7/6.

x = 76

So 1.1666 repeating is 7/6.

It is bigger than 1, so the top is bigger than the bottom.

5 Check

Let's check: 7 divided by 6.

We get 1.1666, and the digits go on the same way.

That is 1.1666 repeating.

So the answer is right!

7 ÷ 6 = 1.1666…

Let's look back.

First: call it x.

Then: move the point.

Then: take away.

Then: remove the 90.

Last: check.

Answer
x = 76

Your turn

Try this one yourself, then check:

Write 1.8333…
Show the answer
116

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