Worked Example 1
Unknown on One Side
38 + □ = 25 + 41
- 1Find the value of the right side: 25 + 41 = 66
- 2Now the equation is 38 + □ = 66.
- 3Think: 38 plus what makes 66? 66 − 38 = 28
Answer: □ = 28
Florida Grade 2 Math · Algebraic Reasoning
MA.2.AR.2.2: Finding the Unknown Number
What this Grade 2 benchmark means, worked examples, common mistakes, and a free printable worksheet.
Created by a Florida mom · Published by Tropical Learning LLC
What Is Benchmark MA.2.AR.2.2?
Students find the missing number in an addition or subtraction equation with three or four numbers. The unknown can be anywhere, even on the left side of the equal sign.
In Grade 2, the unknown is shown with a symbol such as a box (□) or a blank, not a letter. Sums are limited to 100.
Official benchmarkDetermine the unknown whole number in an addition or subtraction equation, relating three or four whole numbers, with the unknown in any position.
How it is tested: Grade 2 students take FAST Star Math, Florida's math test for Kindergarten through Grade 2.
Worked Examples
Worked Example 2
Unknown at the Start
□ − 17 = 45
- 1Some number minus 17 leaves 45.
- 2Add back the 17: 45 + 17 = 62
- 3Check: 62 − 17 = 45
Answer: □ = 62
Common Mistakes to Watch For
Adding the numbers you see
Wrong:□ + 14 = 30, so □ = 44
Think: what plus 14 makes 30? 30 − 14 = 16, so □ = 16.
Ignoring part of the other side
Wrong:12 + □ = 20 + 15, so □ = 8
The right side is 20 + 15 = 35. Then 12 + □ = 35, so □ = 23.
Helpful Math Tip
Always check by putting the number back into the box and seeing if both sides are equal.
Related Grade 2 Skills
Make Florida Math Practice More Fun
Help your child build math confidence with original interactive questions aligned with Florida's B.E.S.T. Mathematics Standards.
Start Practicing FreeIndependent 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.