Checkpoint: sides, angles and the family

Four dots close into four straight sides. Two sides pass through each other. Is it a quadrilateral?

• Yes, because there are four straight sides and the path is closed
• Yes, but only if you redraw it more neatly
• No, because a side cuts through another side

Three corners of a quadrilateral read 85°, 95° and 100°. What is the fourth?

• 80°
• 180°, because the leftovers make a straight angle
• 90°, because a fourth corner is usually square

How many diagonals does a five-cornered shape have?

• 10, because there are ten pairs of corners
• 5
• 2, the same as a quadrilateral

A shape has both pairs of sides parallel. All four sides are 7 long. No corner is 90°. What is its best name?

• Parallelogram, because both pairs are parallel
• Rhombus
• Square, because all four sides are equal

One corner of a parallelogram measures 72°. What is the corner next to it? What is the one across from it?

• Both 72°, because a parallelogram is even all round
• The next-door corner is 288°, because 360 − 72 = 288
• The next-door corner is 108° and the opposite corner is 72°