Rounding and Multiplication

Rounding and Multiplication is a Grade 3 whole-class mental-math activity for estimating products. Students round one or both factors to friendly tens, multiply the rounded numbers mentally, and then compare the estimate with the exact product later. Examples progress from one rounded factor to larger two-factor estimates such as 39 × 48 ≈ 40 × 50.

Use it as a number-sense warm-up when students are learning that estimation can give a quick sense of product size. Comparing the estimate with the exact answer also helps students discuss when rounding creates a close estimate and when it does not. Create a free Find a Math Game account to generate teacher-ready lesson support for Rounding and Multiplication. No credit card, with 3 lifetime lesson generations.