Wyoming Math 2.NBT.5

Math2nd GradeNumber and Operations in Base Ten

The Standard

Add and subtract within 100 using strategies based on place value, properties of addition, and/or the relationship between addition and subtraction.

2023 Wyoming Mathematics Content and Performance Standards · Use place value understanding and properties of operations to add and subtract.

Teacher's field guide

What Students Need to Do: Students break two-digit numbers into tens and ones to add or subtract. They trade between tens and ones when needed and use addition to check subtraction.
What Mastery Looks Like: A student can show why 38 + 27 = 65 by making a new ten from 15 ones. They can solve 52 - 28 = 24 by trading a ten, then check with 24 + 28 = 52.
Common Misconceptions: Some students write 38 + 27 as 515 because they put 5 tens next to 15 ones. Others get 52 - 28 = 36 by subtracting the smaller ones digit from the larger one. Some trade a ten for ones but forget to lower the tens count.
How to Assess It: Exit ticket: Solve 46 + 27 and 73 - 27. Show tens and ones for one problem, then explain how the two answers connect.

Lesson moves

Give pairs base-ten blocks to build 38 + 27, trade ten ones for one ten, and record the total.
Ask students to write two ways to solve 64 - 29, then explain why both ways work.
Draw two number cards from 20 to 49, add them, then check with subtraction; earn a point for both correct equations.
Post a class library count: 63 books, 28 borrowed; students draw tens and ones to find how many remain.

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