Montana Math MT.2.NBT.6

Math2nd GradeNumber and Operations in Base Ten

The Standard

Add up to four two-digit numbers using multiple strategies.

2026 Montana Mathematics Content Standards

Teacher's field guide

What Students Need to Do: Students add up to four two-digit numbers. They use more than one method, such as pairing numbers to make tens or adding tens and ones separately.
What Mastery Looks Like: Students get the same total using two methods. They show when ten ones become one ten and can explain why they chose particular pairs.
Common Misconceptions: Some students add only two numbers and overlook the others. Others forget to add regrouped tens to the total or think they must add the numbers in the order given.
How to Assess It: On an exit ticket, ask students to solve 38 + 34 + 16 + 22 by pairing numbers, then by adding tens and ones. Ask them to mark where they regroup.

Lesson moves

Build 38, 34, 16, and 22 with base-ten blocks, then trade ten ones for a ten as students find the total.
Ask, "Which two numbers would you add first in 38 + 34 + 16 + 22, and why?" Have students write their reasons.
Deal partners four cards labeled 10 to 49; give one point for a correct sum and another for a different method.
Label four book bins 38, 34, 16, and 22; ask students to find the total number of books two ways.

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