The places to the right of the decimal point have names that mirror the names of the whole number decimal places. The first number to the right of the decimal point represents tenths, the second represents hundredths, the third represents thousandths, and so on for ten-thousandths, etc. [2] X Research source For example, in the number 2. 37589, “2” is the number of ones, “3” is the number of tenths, “7” is the number of hundredths, “5” is the number of thousandths, “8” is the number of ten-thousandths, and “9” is the number of hundred-thousandths.
For example, if you are asked to round to the nearest thousandth in the number 12. 9889, you would start by finding the thousandths place. Counting from the decimal point, the spaces to the right represent tenths, hundredths, thousandths, and ten-thousandths, so the second “8” (12. 9889) is the one you want. Sometimes, instructions will tell you exactly which decimal place to round to (e. g. , “round to the third decimal place” means the same thing as “round to the nearest thousandth”).
In our example number (12. 9889), you’re rounding to the thousandths place (12. 9889), so now look at the number to the right of this, which is the final “9” (12. 9889).
In the example number (12. 9889), since the final 9 is higher than 5, round your thousandths place up. The rounded value becomes 12. 989. Note that you drop the digits after the rounded decimal place.
You wouldn’t round 12. 9889 down because the final 9 isn’t 4 or lower. However, if you were working with the number 12. 9884, you could round it down to 12. 988. Does this process seem familiar? If so, it’s because this is basically how you round whole numbers — the decimal point doesn’t change things.
In other words, start at the ones place, then look at the number to the right. If this number is 5 or greater, round up. If it is 4 or lower, round down. The decimal point in the middle doesn’t change anything. For example, if you needed to round the example number from earlier (12. 9889) to the nearest whole number, you’d start by looking at the ones place: 12. 9889. Since the “9” to the right is greater than 5, you would round up to 13. Since you’ve gotten a whole number answer, you don’t need the decimal point any more.
For example, if you receive the instructions “Round 4. 59 down to the nearest tenth”, you’d round the 5 in the tenths place down even though the 9 to the right means you’d normally round it up. This would give you 4. 5. Similarly, if you are told to “round 180. 1 up to the nearest whole number,” you’d round to 181 even though you’d normally round down.
First, find the hundredths place. This is two spaces to the right of the decimal point, or 45. 783. Then, look at the number to the right: 45. 783 Since 3 is less than 5, round down. This gives an answer of 45. 78.
Find the third decimal place. This is 6. 2979. Look at the number to the right. This is 6. 2979. Since 9 is greater than 5, round up. This gives an answer of 6. 298.
Find the tenths place. This is 11. 90. Look at the number to the right. This is 11. 90. Since 0 is less than 5, round down. This gives an answer of 11. 9.
Find the ones place. This is -8. 7 Look at the number to the right. This is -8. 7. Since 7 is greater than 5, round up. This gives an answer of -9. Leave the negative sign as-is.
