Rounding a number means changing its value to a number that is closer to a certain level of precision or a certain place value. When we round a number, we usually specify the level of precision or place value that we want the rounded number to have. For example, we might want to round a number to the nearest whole number, to the nearest tenth, or the nearest thousandth.
The process of rounding involves looking at the digit in the place value that we want to round to and using the digit to the right of it to determine whether to round up or down.
Rules of Rounding:
- If the digit to the right of the place we are rounding to is 5 or greater, we round up.
- If the digit to the right of the place we are rounding to is less than 5, we round down.
The place values to the right of the decimal point, or the right of one's place in number, are called decimal places. The decimal places are numbered starting from the tenth place, which is one place to the right of the decimal point. The next place to the right is the hundredth place, followed by the thousandth place, and so on.
The third place to the right of zero is the thousandth place. When rounding to the nearest thousandth we have to look at the fourth decimal place to see whether it must be rounded up or down. The fourth digit is an 8 which is greater than 5. So we must round the thousandth place up.
This gives us 0.143, rounded to the nearest thousandth.