Compare the problems: what changed?
Compare two related problems, predict how the solution changes, and solve the changed one.
- Germany: grade 4
- Ukraine: grade 3
- Russia: grade 3
Guide
Ukrainian Grade 3-4 books often end a problem with: "Compare problems 1 and 2. What changed? How will the change affect the solution of problem 2?" The question, the numbers or the situation may change, and then the plan changes: a new action appears, one disappears or an action is replaced by its inverse.
Example. Problem 1: "Dad gave 3 notes of 2 UAH and mum gave 5 UAH." Problem 2: "...and mum gave 5 notes of 1 UAH." One more action is needed: 5 · 1 = 5. The answer is the same, but the solution is longer.
You can also make an inverse problem: what was asked becomes known and one known number becomes the unknown. "16 boys, 7 fewer girls. How many girls?" becomes "16 boys, 9 girls. How many fewer girls?"