Planimetry review
Answers are for parents and teachers.
1
How many degrees is an interior angle of a regular decagon?
144
2
The apex angle of an isosceles triangle is 40°. How many degrees is a base angle?
70
3
One angle of a parallelogram is 3 times another. How many degrees is the smaller angle?
45
4
A chord of length 24 cm lies 9 cm from the centre of a circle. Find the radius.
R = √(12² + 9²) = √225 = 15 cm.
5
The circle circumscribed about a square has radius 6√2 cm. Find the radius of the circle inscribed in that square.
Diagonal = 2R = 12√2 cm, side = 12 cm, inscribed radius = 12/2 = 6 cm.