This skill involves interpreting an equation as a statement that two quantities are equal and finding an unknown addend in whole-number addition equations within 100, whether the unknown appears before or after the known addend. Learners reason that subtraction can undo addition and use relationships among parts and the total, including related fact families, to determine and check the missing number; multi-step equations, negative numbers, and generalized symbolic algebra are outside this scope.
An addition equation shows that both sides have the same value. To find a missing addend, subtract the known addend from the total.
Example:
Click a topic below to practice the foundational skills you'll need, learn the steps, or master this skill
Earned ?