Unit 2, Lesson 20# Estimate differences by rounding and apply to solve measurement word problems

EngageNY 60 min(s)

In this lesson, students estimate the differences of two numbers by rounding both subtrahends to either the nearest then or hundred, and then compare their estimates to the actual difference. For example, they estimate 362 - 189 by rounding to the nearest hundred (400 - 200 = 200) and the nearest ten (360 - 190 = 170). Then they calculate the actual sum and determine which estimating method was more accurate. They also investigate why estimates of differences like 349 - 154 and 349 - 149, when rounding to the nearest hundred, are so far apart.