NY Next Generation Math NY-1.OA.4

Math1st GradeUnderstand and apply properties of operations and the relationship between addition and subtraction.

The Standard

Understand subtraction as an unknown-addend problem within 20.

New York State Next Generation Mathematics Learning Standards

Teacher's field guide

What Students Need to Do: Students understand subtraction within 20 as finding a missing addend. They connect a subtraction equation to an addition equation with an unknown part.
What Mastery Looks Like: A student solves 13 minus 8 by asking what number added to 8 makes 13. The student shows that 8 + 5 = 13, so 13 - 8 = 5.
Common Misconceptions: Students may count backward inaccurately or reverse the known part and total. They may write a related addition fact whose numbers do not match the subtraction equation.
How to Assess It: Ask students to solve 15 minus 9 by writing a related unknown-addend equation and explaining how it gives the difference.

Lesson moves

Hide part of a counter set under a cup, show the total and visible part, and find the hidden addend.
Ask students to explain how the unknown-addend equation 7 + blank = 12 helps solve 12 minus 7.
Play fact-family match with subtraction equations, unknown-addend equations, and counter models within 20.
Find how many seats are empty when the total seats and occupied seats are known.

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