Florida B.E.S.T. MA.2.AR.2.2

Math2nd Grade

The Standard

Determine the unknown whole number in an addition or subtraction equation, relating three or four whole numbers, with the unknown in any position.

Florida B.E.S.T. Standards for Mathematics

Teacher's field guide

What Students Need to Do: Students find a missing number that makes an addition or subtraction equation true, even when the blank appears first or between numbers. They use related facts, models, or inverse operations, then check both sides.
What Mastery Looks Like: Students solve equations such as 12 − □ = 5, □ + 8 = 17, and 7 + 6 = 9 + □. They explain their strategy and substitute the number to verify both sides are equal.
Common Misconceptions: Students may treat the equal sign as a signal to calculate only what comes before it. They may subtract the smaller number from the larger number regardless of position. Some guess a missing number without checking the full equation.
How to Assess It: Give this exit ticket: solve 18 − □ = 7, □ + 9 = 23, and 6 + 8 = 9 + □. Ask students to check each answer.

Lesson moves

Use counters and equation mats to model 14 − □ = 8, then remove counters until both known amounts are represented.
Ask students to explain in writing how addition can help solve □ − 7 = 11.
Play equation match with cards showing missing-number equations and separate cards showing their solutions.
Present a snack problem: 18 crackers were packed, some were eaten, and 10 remain; write and solve an equation.

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