Rounding decimals to whole numbers

Rounding a decimal means finding the closest friendly number. When you round to the nearest one, you are picking the closest whole number.

Here is how to do it. First, look at the digit in the tenths place. That is the first digit after the decimal point. If it is 5 or more, round the ones digit up. If it is less than 5, keep the ones digit the same.

Try 7.6. The tenths digit is 6, and 6 is 5 or more, so 7.6 rounds up to 8. Now try 7.2. The tenths digit is 2, and 2 is less than 5, so 7.2 rounds down to 7.

What about 7.5? It sits exactly halfway between 7 and 8. The rule is that halfway numbers round up, so 7.5 rounds to 8.

A number line can help you see it. Put 7 and 8 on the line. Any number from 7.0 up to 7.4 is closer to 7. Any number from 7.5 up to 7.9 is closer to 8. Once you know the rule, you can round any decimal with one decimal place in just a few seconds.

A decimal is a way to show part of a whole. In the number 6.4, the 6 is in the ones place and the 4 is in the tenths place. That means 6.4 is 6 whole ones and 4 tenths.

You can mark decimals on a number line. The number 6.4 goes between 6 and 7, a little less than halfway along. The number 6.5 goes exactly halfway. The number 6.9 goes almost all the way to 7.

Rounding to the nearest whole number means finding which whole number the decimal is closest to. Look at the tenths digit. If it is 4 or less, the decimal is closer to the lower whole number, so round down. If it is 5 or more, it is closer to, or halfway to, the higher whole number, so round up.

So 6.4 rounds to 6, 6.5 rounds to 7, and 6.9 rounds to 7. You can use this to make quick estimates in real life, like guessing that a puppy weighing 4.6 kilograms weighs about 5 kilograms.

A decimal is an in-between number. It lives between two whole numbers, like 3.7 lives between 3 and 4.

The digit right after the decimal point tells you which tenth you have. In 3.7, the 7 means 7 tenths. Think of a chocolate bar cut into 10 equal pieces. 3.7 is 3 whole bars plus 7 of those small pieces.

Now here is a neat trick. Half of 10 pieces is 5 pieces. So when the tenths digit is 5 or more, you have half or more of the way to the next whole number. That is when you round up. When the tenths digit is 4 or less, you are less than halfway there, so you round down.

That is the whole rounding rule: 5 or more, round up. 4 or less, round down. It works for every decimal with one decimal place, like 2.4 rounding to 2 and 2.5 rounding to 3.