Question 1

We will determine the correct word for each blank based on the definitions of similarity and congruence.

Step 1 — Understand similarity and congruence Congruent figures have the same shape and size. Similar figures have the same shape but can have different sizes.

Step 2 — Determine the correct words For (i): All circles have the same shape but can have different radii. Thus, they are similar.

For (ii): All squares have the same shape (all angles are $90^\circ$ and the ratio of corresponding sides is always equal) but can have different side lengths. Thus, they are similar.

For (iii): Equilateral triangles always have the same shape because all their angles are $60^\circ$. Isosceles triangles can have different angles and shapes. Thus, all equilateral triangles are similar.

For (iv): By definition, two polygons of the same number of sides are similar if: (a) their corresponding angles are equal, and (b) their corresponding sides are proportional.

Answer

(i) similar (ii) similar (iii) equilateral (iv) (a) equal, (b) proportional