Maryland Math 1.NOS.E.12.b

Math1st GradeNumber and Operation Sense

The Standard

1.NOS.E.12: Subtract a multiple of 10 from another multiple of 10 within 90.

Use counting strategies, properties of operations, and/or the inverse relationship between addition and subtraction to subtract.

Maryland College and Career Ready Standards for Mathematics (2025) · USE PLACE VALUE UNDERSTANDING AND PROPERTIES TO ADD AND SUBTRACT.

Teacher's field guide

What Students Need to Do: Students subtract by counting back, counting up, or using an addition fact they know. They show their steps with counters, a number line, or an equation.
What Mastery Looks Like: A student can solve 13 - 5 by counting back five steps or thinking, '5 plus what makes 13?' They get 8 and check that 8 + 5 = 13.
Common Misconceptions: Students may count 13 as the first backward step and land on 9 instead of 8. Some check 13 - 5 by adding 13 + 5, rather than adding 8 + 5.
How to Assess It: Exit ticket: Solve 14 - 6. Show your steps, then write an addition equation that checks your answer.

Lesson moves

Give pairs 12 counters and have them remove 5, count what remains, and write a subtraction and an addition equation.
Ask, 'How can 6 + 7 help you solve 13 - 6?' Have students explain with a drawing.
Play subtraction match: students pair cards like 11 - 4 and 4 + 7 = 11, then explain each match.
Set out 10 pencils, put 3 in a cup, and ask how many remain and how to check by adding.

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