The congruence and similarity proof sheets hide one reason and let a child choose it; this is the next step, where the table is empty and the whole argument is theirs to write. A diagram, a Given, a Prove — and room to build the proof from nothing.
If they get stuck
The answer key prints on a separate page.
Choosing a reason from a bank is the on-ramp; writing the proof is the destination, and the two are meant to sit side by side — scaffold with one, assess with the other. Each figure here is one of the known-correct proofs the choice sheets use, so a teacher who has taught them recognizes every one, but the child meets it as a blank two-column table with only the Given, the Prove, and the picture to start from.
This is a written worksheet, not an online exercise, for the same reason the puzzle sheets are: a proof has many valid orderings and wordings, so it cannot mark itself. The answer key is the model — every statement and the reason it rests on, written out in full — which is exactly what a child checks their own argument against.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Write a triangle proof, step by step