Estimation is the ability to find an approximate answer quickly, without calculating exactly. This skill is used constantly in everyday life — estimating grocery totals, travel times, project costs, and whether an answer seems reasonable.

The most common estimation strategy is rounding first, then calculating. To estimate 48 + 73, round to 50 + 70 = 120. To estimate 6 × 38, round to 6 × 40 = 240. The estimate should be close to the exact answer without requiring precise calculation.

Estimation is essential for checking work. If a student calculates 47 × 8 = 846 but estimates 50 × 8 = 400, they know their exact answer must be wrong. This error-checking habit prevents careless mistakes and builds mathematical confidence.

As students advance, they estimate with decimals, fractions, and larger numbers. The key principle remains the same: simplify the numbers to make the calculation easy, then use the estimate to verify or approximate the exact answer.