Attributes of Shapes — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. An octagon has 8 vertices.
'Oct' means eight, like the eight legs of an octopus, so an octagon has 8 sides and 8 corners — the shape of a stop sign.
2. An angle smaller than a right angle is called an acute angle.
An acute angle measures less than 90 degrees, making it look pinched and pointy — a helpful trick is to picture an 'a-cute' little angle.
3. An angle larger than a right angle is called an obtuse angle.
An obtuse angle is wider than 90 degrees, so the two rays open up much further apart, giving the angle a wide and blunt look.
4. A heptagon has 7 sides.
'Hepta' is the Greek root for seven, so a heptagon is the polygon with exactly 7 straight sides — one more than a hexagon.
5. A shape with all equal sides and all equal angles is called a regular polygon.
A regular polygon follows a strict, even pattern in which every side has the same length and every angle has the same measure — like a square or an equilateral triangle.
6. Perpendicular lines form a right angle where they meet.
Perpendicular is the special name for lines that cross to make a perfect square corner, and that 90-degree corner is called a right angle.
7. A square has 2 pairs of perpendicular sides.
A square's top and bottom each meet the left side at right angles, and they each meet the right side at right angles too — that gives 2 pairs of perpendicular sides.
8. The number of vertices in a polygon equals the number of sides.
Each side of a polygon ends at a corner, and each corner is shared by exactly two sides — so the count of sides and vertices is always the same.
9. A nonagon is a polygon with 9 sides.
'Nona' comes from the Latin word for nine (think 'November,' which used to be the ninth month), so a nonagon has exactly 9 sides.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Decagon
→ 10 vertices
4 vertices
Heptagon
→ 7 vertices
9 vertices
Nonagon
→ 9 vertices
10 vertices
Quadrilateral
→ 4 vertices
7 vertices
Correct matches: Decagon → 10 vertices; Heptagon → 7 vertices; Nonagon → 9 vertices; Quadrilateral → 4 vertices.