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Compare 1/3 and 0.3

Step by step, with the reason for every step · Ordering mixed numbers and repeating decimals · Foundations

Step by step

The question

Question: compare 1/3 and 0.3.

13 and 0.3

1 Write it as a decimal

To compare, we write every number the same way: as a decimal.

The bottom 3 does not go into 10, 100 or 1000.

So we divide: 1 divided by 3, one digit at a time.

= 13 = 1 ÷ 3 = 0.333…

10 divided by 3 is 3, with 1 left.

1 left again: the 3 repeats for ever.

So 1/3 is 0.333….

10 ÷ 3 = 3, 1 left: the 3 repeats

Careful!

1/3 is not 0.3.

Its 3s go on for ever, so it is a bit more than 0.3.

Careful: not 13 = 0.3 ✗

2 Same number of digits

Zeros at the end of a decimal do not change it: 0.3 is the same as 0.300.

A repeating decimal goes on for ever, so we can write as many of its digits as we need.

So we give every number 3 digits after the point.

= 0.333…, 0.300

3 Compare

Now both have 3 digits after the point.

So we can forget the point and compare them like whole numbers: 300 < 333.

= 0.300 < 0.333…
300 < 333

4 Write the answer

Now with the numbers as they were given: 1/3 > 0.3.

1/3 is greater than 0.3.

= 13 > 0.3

5 Check

Let's check on a number line.

Smaller numbers are further to the left.

We put a dot for each number.

From left to right: 0.3, 1/3.

The same order.

So the answer is right!

left to right: same order

Let's look back.

First: write it as a decimal.

Then: same number of digits.

Then: compare.

Then: write the answer.

Last: check.

Answer
= 13 > 0.3

Your turn

Try this one yourself, then check:

23 and 0.6
Show the answer
23 > 0.6

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