Number

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Decimal Places

Rounding to a number of decimal places gives us the opportunity to simplify complicated numbers after the decimal point.

Rounding decimals to a number of decimal places allows us simplify numbers, while reducing their accuracy. This helps to make numbers more readable in everyday contexts.

Rounding to decimal places follows the same rules as rounding whole numbers. If a digit is greater than 5, then we round up the digit to the left. If the digit is less than 5, the we round down the digit to the left.

For example, let's try rounding $23.45357$ to 3 decimal places

Choose the number to round

As we are looking to round to 3 decimal places, we need to round the 3rd digit after the decimal point: $23.45{\color{#21affb}3}57$

Look at the digit to the right of it

The digit to the right controls whether it rounds up or down. As 5 is 5 or greater, we need to round up ⬆️

Round up the 3rd digit after the decimal

$23.45{\color{#21affb}3}57$ rounds up to $23.45{\color{#21affb}4}$

Let's try rounding to 2 decimal places

To 2 decimal places, we need to round the 2nd digit after the decimal point $23.4{\color{#21affb}5}357$

Look at the digit to the right

This time, the digit to the right is 3, which is less than 5. This means that we do not round the 2nd digit at all.

Cut off the decimal after the 2nd decimal place

To 2 decimal places, $23.4{\color{#21affb}5}357$ rounds to $23.4{\color{#21affb}5}$

Nice! 🤟

Amazing work!

Round $23.4543$ to 3 decimal places

Round $45.483$ to 2 decimal places

What if we wanted to round $0.999$ to 2 decimal places? We need to round up, but what do we round up to?

Let's try rounding $0.999$ to 2 decimal places

Look at the number

$0.9{\color{#21affb}9}9$ indicates that we need to round up the 9

Round the 9 up

9 rounds up to 10, so it also affects the digit to the left. So, $0.999$ becomes $1.00$ as there are two 9's. We keep the two 0's so that the number keeps 2 decimal places.

Nice! 🙌

$0.999$ to 2 decimal places is $1.00$

Let's try rounding $0.899$ to 2 decimal places

This time, there is only one 9. Therefore, we round up in the same way, but this time the answer is $0.90$

What is $0.798$ to 2 decimal places?

What is $0.395$ to 2 decimal places?