Montana Math MT.1.OA.1
The Standard
Use addition and subtraction within 20 to solve problems of all types. This standard should incorporate cultural context relating to Montana Indigenous Peoples and local communities.
2026 Montana Mathematics Content Standards
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students solve addition and subtraction stories with numbers to 20. They find missing starting amounts, changes, totals, parts, and differences. They show their thinking with objects, drawings, or equations.
What Mastery Looks Like
- A student can find how many books were on a cart before six were added, if there are 14 now. They can compare two groups, find how many more one has, and explain their answer.
Common Misconceptions
- Some students add 12 and 5 when a story says five of 12 items were taken away. Others answer 12, not four, when asked how many more 12 is than eight. They may assume the missing number must come at the end of an equation.
How to Assess It
- Exit ticket: 'A library cart had some books. Six were added, and now it has 14. How many were there first?' Ask students to show a drawing or equation.
Lesson moves
Ways to Teach It
Give pairs counters to model a cart that ends with 14 books after six are added, then have them find its starting amount.
Ask, 'One shelf has 12 books and another has eight. How many more are on the first shelf?' Discuss two ways to show it.
Play Missing Number Bingo: call 'I gave away five stickers and have nine left'; students cover 14.
Show a public flyer for a Montana tribal community event, then ask how many more chairs are needed if seven of 15 are set out.
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Printable MT.1.OA.1 Worksheet
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