Five pages on estimating sums and differences within 100. Page 1 starts with six number line pieces from one ten to the next: students circle the ten each number is closer to, then add tens that are already rounded, such as 40 + 30. Page 2 has a 0 to 100 number line at the top and ten addition problems: round each number to the nearest ten, then add the tens. Page 3 does the same with subtraction. On page 4 eight children share their answers; students estimate each one and circle makes sense or does not make sense. Page 5 has four word problems that ask about how many, with two answers to choose from, and one bus problem where the estimate is too close to tell, so students add to check.
Before page 1, draw a number line from 30 to 40 on the board and stand a student on 38: is it a shorter walk to 30 or to 40? Do the same with 33. On page 4, ask students to explain how they knew an answer did not make sense, then find the mistake together. The bus problem on page 5 makes a good class talk: when is an estimate good enough, and when do you need the exact answer?
Estimate at the store: if one snack costs 38 cents and another costs 21 cents, about how much is that? Round each price to the nearest ten and add. Then check with the exact amount. Ask your child whether a quick estimate tells you if 80 cents is enough.
This pack supports the following Common Core State Standards for Mathematics:
© Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
A 5-page estimating pack for 2nd grade. Find the closer ten on a number line, then estimate sums and differences within 100 by rounding each number to the nearest ten and adding or subtracting the tens. Estimate to check whether a child's answer makes sense, and solve word problems that ask about how many, including one where the estimate is too close to tell and the exact sum decides. Every page comes in color and in black and white. Answer keys included.
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