Draw a graph for the radius and circumference of circle using a suitable scale.
(Hint : Take radius = 7,14,21 units and so on) From the graph,
A) Find the circumference of the circle when radius is 42 units.
B) At what radius will the circumference of the circle be 220 units?
Circumference = 2
r
The circumference of a circle depends on the radius of a circle.
So, we plot the circumference on the y-axis as it is the dependent variable and the radius on the x-axis as it is the independent variable.
∴ We get the equation in terms of x and y as
y = 2
x
When x = 0,
y = 2
× 0 = 0
When x = 7,
y = 2
× 7 = 2 × 
× 7 = 44
When x = 14,
y = 2
× 14 = 2 × 
× 14 = 88
When x = 21,
y = 2
× 21 = 2 × 
× 21 = 132
The points in the graph are given as
A = (0, 0)
B = (7, 44)
C = (14, 88)
D = (21, 132)
The line segments are
A) When the radius is 42 units, i.e. x = 42,
y = 264 (from the graph)
B) The circumference of the circle will be 220 units when the radius is 35 units (from the graph)