\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)

Rounding

Rounding


Imagine you have 29 marbles. To quickly tell a friend, you might say, "I have about 30 marbles." This is rounding!
We round numbers to:
  • Make calculations easier.
  • Make numbers simpler to understand and remember.

Method Rounding Numbers to a Place Value
  1. Find the digit in the place you are rounding to.
  2. Look at the digit to the right of it.
  3. If this digit is 5 or more, add 1 to the digit in the place you are rounding to (round up).
  4. If this digit is 4 or less, keep the digit the same (round down).
  5. Replace all digits to the right with zeros.
Example
Round the number \(365\) to the nearest hundred.

$$\begin{aligned}[t]&\textcolor{colordef}{\underline{3}}65 && \text{Find the digit in the hundreds place: } \textcolor{colordef}{3}\\&\textcolor{colordef}{3}\textcolor{colorprop}{\underline{6}}5 && \text{Look at the digit to the right: } \textcolor{colorprop}{6}\\&&&\text{Since } \textcolor{colorprop}{6} \text{ is greater than 5, round up by adding 1: } \textcolor{colordef}{3}+1 = \textcolor{olive}{4}\\&\textcolor{olive}{4}\textcolor{purple}{00} && \text{Replace all digits to the right with zeros.}\end{aligned}$$The rounded number is \(400\).