Examples, solutions, and videos to help Grade 3 students learn how to estimate sums and differences of measurements by rounding, and then solve mixed word problems.
Common Core Standards: 3.NBT.2, 3.NBT.1, 3.MD.1, 3.MD.2
New York State Common Core Math Grade 3, Module 2, Lesson 21
Grade 3, Module 2, Lesson 21 Worksheets
Gloria fills water balloons with 238 mL of water. How many milliliters of water are in 2 water balloons? Estimate to the nearest 10 mL and 100 mL.
Which gives a closer estimate?
Note: This problem reviews Lesson 17 by having students round to estimate sums and then calculate the actual answer. It reviews addition because this lesson includes mixed practice with addition and subtraction.
Each table has the premeasured items and measurement tools listed below. Students work together to measure weight, length, and capacity.
Next, they round to estimate sums and differences, then use the standard algorithm to solve.
Materials Description (per table)
Problem 1: 1 digital scale, 1 bag of rice premeasured at 58 grams, 1 bag of beans premeasured at 91 grams
Problem 2: 1 meter stick, labeled Yarn A, B, and C (Yarn A premeasured at 64 cm, Yarn B premeasured at 88 cm, Yarn C premeasured at 38 cm)
Problem 3: 1 400-milliliter beaker, Container D premeasured at 212 mL, Container E premeasured at 238 mL, Container F premeasured at 195 mL
Problem 4: No additional materials
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