Study guide: Find Unknowns in Addition and Subtraction Stories
Represent a missing change, a missing start, a comparison, and a balanced equation.
Ideas to explain in your own words
- A change story can give the start and finish while leaving the added amount unknown.
- When items leave, the start was larger than the remaining amount.
- A comparison asks about the difference between two groups, not their combined total.
- An equation can have a missing amount on either side.
Useful vocabulary
- unknown
- An amount that has not been stated.
- equation
- A sentence saying two expressions have equal values.
Watch your reasoning
- The final total is not the number added.
- Do not subtract the removed part from the leftovers.
- Together and how many more ask different questions.
- The blank may be a part, rather than the entire total.
A worked review example
A tray starts with 6 counters and ends with 14. The unknown change is 14−6=8. Counting on eight from six reaches fourteen. Check 6+8=14; this confirms the change without confusing it with the final total. Label the start and finish before choosing an operation. The final total is not the number added. Draw one bar for the final total and split off the starting part.
Make a practice plan
- Find How Many Were Added: A shelf starts with 7 cards and ends with 18. Expected: 11 added.
- Find a Starting Amount Before Some Leave: Six are removed and nine remain. Expected: the starting amount was 15.
- Find How Many More in a Comparison: Compare 16 and 9 cards. Expected: the larger group has 7 more.
- Find the Number That Balances an Equation: Solve 9+6=10+__. Expected: 5.