Mathematics Chapter 9 Lesson 1

Question 1

What is the formula for the radius of a circle?

Answer 1

Radius = Diameter / 2

The radius is half the length of the diameter.

Question 2

What is the formula for the diameter of a circle?

Answer 2

Diameter = 2 x Radius

The diameter is twice the length of the radius.

Question 3

If the diameter of a circle is 20 cm, what is the radius?

Answer 3

10 cm

Calculated using the formula: Radius = Diameter / 2.

Question 4

What is the circumference (C) of a circle in terms of diameter (d)?

Answer 4

C = πd

This can also be expressed as C = 2πr where r is the radius.

Question 5

What is the formula for the circumference of a circle in terms of radius (r)?

Answer 5

C = 2πr

π (pi) is approximately 3.14.

Question 6

What is the circumference of a circle if the radius is 2 cm?

Answer 6

12.56 cm

Calculated using C = 2πr: C = 2 x 3.14 x 2.

Question 7

What is the circumference of a circle if the diameter is 2 cm?

Answer 7

6.28 cm

Calculated using C = πd: C = 3.14 x 2.

Question 8

True or False: The circumference of a circle can be calculated using either radius or diameter.

Answer 8

True

Both formulas for circumference are valid.