⁦Compare the problems⁩: ⁦what changed⁩?

⁦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?"