First Grade · Math · week 22

Story problems: change unknown

Solve word problems where the change is unknown, using a missing addend or subtraction.

In a "change unknown" story, you know how many you started with and how many you ended with, but not what happened in between. "Maya had 5 apples, then got some more, and now has 9. How many did she get?"

These stories often turn into a missing-addend equation: 5 + ___ = 9. Count on from the start to the end to find the change.

📋 For the teacher
Teach it (10–15 min):
  • Underline or point to the starting number and the ending number first -- the change is what is left to find.
  • Use counting on, from start to end, as the go-to tool for change-unknown addition stories.
  • Act out the story: start with objects, hide some more being added, reveal the end amount, then figure out how many were hidden.
  • Keep numbers small enough to count on comfortably.
Talk about it:
  • In a change-unknown story, what two numbers do you already know?
  • How does counting on help find the missing change?
  • Can you tell a change-unknown story about something at home?

Mastery looks like: They identify the start and end amounts in a story and find the missing change using counting on or subtraction.

Common stumbles: Confusing the start and end amounts; adding the start and end together instead of finding the difference.

See it visually

Interactive, spoken-aloud tools that show this idea in motion.

SubtractionTake away and count back, step by step.try →
Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Math for this learner.
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