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A decimal is a way of writing a number that is not whole.

We place digits to the left or right of the decimal point depending on their value. On the left we have the hundreds, tens and ones and on the right we have the tenths and hundredths.

Let's have a look at the number 41.32.

Rounding is important because it makes numbers easier to manage and allows us to estimate answers.

Imagine you’re in a shop and you need to quickly estimate how much your shopping will be before you get to the till. You would round up the prices, like £1.99 to £2.00, to make it easier to add up.

Always look at the digit to the right of the one you’re supposed to be rounding to:

• if it is 5 or more, then round it up
• if it is less than 5, then round down

Now take a trip to the shops with Jerry and Albert and find out how prices can be rounded with this KS2 Maths video.

If you are rounding decimals to the nearest tenth, which column would you be looking at to decide whether to round up or down?The hundredths column as it’s to the right of the tenths.

Round 12.32 to the nearest tenth.

The digit in the hundredths column is a 2, so we round down to 12.3

Round 19.79 to the nearest tenth.

9 is in the hundredths, so we round up to 19.8.

We can also use a number line to help visualise rounding decimals to the nearest tenth. Take a look at the number line below.

Can you use the number line to round 3.24 to the nearest tenth?

The number line shows the position of 3.24 between 3.2 and 3.3.

Can you see that 3.24 rounded to the nearest tenth is 3.2

When you have to round a decimal to the nearest **whole number,**you have to think about the ones column.

The column to the right of the ones column is the tenths, so that is the column you use to decide whether to round up or down.

What is 9.49 rounded to the nearest whole number?

4 is in the tenths column, so you have to round down to 9.

Round 123.99 to the nearest whole number.

Since the digit in the tenths column is 9, we round up 123.99 to 124.

Let's take a look at this on a number line again.

Can you use the number line to round 3.24 to the nearest whole number?

This time you can see the position of 3.24 between 3 and 4.

Can you see that 3.24 rounded to the nearest whole number is 3.

Jerry and Albert's shopping list

Have a go at rounding some prices for items on Jerry and Albert's shopping list.