Every polygon's angles add to a number you can work out rather than look up. These free printable worksheets ask for the total for a shape with a given number of sides, and sometimes for the size of a single angle in a regular one.
If they get stuck
The answer key prints on a separate page.
The rule comes from triangles. Any polygon can be cut into triangles from one corner — a pentagon gives three, a hexagon gives four — and each triangle contributes 180°. That is where (n − 2) × 180 comes from, and a child who has drawn the cuts once can rebuild the formula whenever they need it rather than remembering it wrong.
The second question is a division and a trap in equal measure. One angle of a regular hexagon is 720 ÷ 6 = 120°, and the division only works because the shape is regular. Both kinds of question appear on the page so a child has to read which is being asked rather than apply the same move eight times.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Angles in a polygon, step by step