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Florida Grade 1 Math · Algebraic Reasoning

MA.1.AR.2.3: Finding the Missing Number

What this Grade 1 benchmark means, worked examples, common mistakes, and a free printable worksheet.

Created by a Florida mom · Published by Tropical Learning LLC

Download Free Worksheet (PDF)See worked examples

What Is Benchmark MA.1.AR.2.3?

Children find the missing number in an addition or subtraction equation with three numbers. The missing number can be anywhere, even on the left side of the equal sign.

In Grade 1, the missing number is shown with a box (□) or a question mark, not a letter. Sums are up to 20.

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

How it is tested: Grade 1 students take FAST Star Math, Florida's math test for Kindergarten through Grade 2.

Worked Examples

Worked Example 1

Missing Addend

8 + □ = 14
  1. 1Think: 8 plus what makes 14?
  2. 28 + 6 = 14
Answer: □ = 6

Worked Example 2

Missing Starting Number

□ − 4 = 9
  1. 1Some number take away 4 leaves 9.
  2. 2Add the 4 back: 9 + 4 = 13
  3. 3Check: 13 − 4 = 9
Answer: □ = 13

Common Mistakes to Watch For

Subtracting the numbers you see

Wrong:□ − 4 = 8, so □ = 4

Take 4 away from the missing number and you get 8, so the missing number is 8 + 4 = 12.

Thinking the equation is backwards

Wrong:17 = □ + 5 can't be solved because 17 comes first.

Read it as "□ + 5 is the same as 17." 12 + 5 = 17, so □ = 12.

Helpful Math Tip

Put the number back in the box and check that both sides match.

Related Grade 1 Skills

MA.1.AR.2.1

Subtraction as a Missing Addend

MA.1.AR.2.2

True or False Equations

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Independent Educational Platform. FastChomp is published by Tropical Learning LLC and is not affiliated with, sponsored by, or endorsed by the Florida Department of Education. FAST and Star assessment names are referenced for informational purposes only. FastChomp practice questions are original educational materials, not official Florida FAST assessment questions.