Rounding is the process of replacing a number with a nearby number that is simpler to work with. We round numbers to estimate quickly, communicate approximate values, and check whether our exact calculations are reasonable.

The basic rule for rounding is to look at the digit to the right of the place you are rounding to. If it is 5 or greater, round up. If it is less than 5, round down. For example, 47 rounded to the nearest ten is 50, while 43 rounds to 40.

Rounding extends to larger numbers and decimals. Rounding 2,847 to the nearest hundred gives 2,800. Rounding 3.67 to the nearest tenth gives 3.7. Each context determines the appropriate level of precision.

Rounding is the foundation of estimation, which is critical for checking work and making quick calculations. When students can quickly round and estimate, they develop better number sense and can catch errors in their exact calculations.