Free Circles 02 Practice Test - 4th Grade 

The line PQ is the diameter of the circle. A diameter of a circle is a line segment that passes through centre of the circle and whose endpoints lie on the circle.

Diameter = 2 $\times$ radius (or) twice the radius 
$\therefore$ D = 2r is the correct relation between them.

The shaded triangle in the figure is an isosceles triangle.
A triangle in which two sides are equal is called an isosceles triangle. Here, the two equal sides are the radii of the circle OA and OB.

The chords of the given circle are AB, CD, BC and AD.

The diameter of a circle is its longest chord.

Since BC and AD pass through the center(O) of the circle, they are the diameters of the circle and hence, the longest chords.

Given that

The radius of a circle is 4 cm.

The diameter of the circle = 4 $\times$ 2 = 8 cm

The diameter is the longest chord of a circle. Hence, the length of any chord cannot be more than 8 cm.

The radius of a circle is a line segment joining the center of the circle to any point on the circumference of the circle.

The line segment OA is the radius of the circle.

Given that

The radius of a circle = 48 cm

The diameter of a circle = radius $\times$ 2

On substituting the values we get;

The diameter of the circle = 48 $\times$ 2 = 96 cm

Given that

The length of the diameter of a circle = 36 cm

We know that, radius of a circle = $\frac{Diameter}{2}$

On substituting the values we get:

Radius of circle = $\frac{36}{2}=18cm$ 

Given that

The radius of the circle = 18 cm

The diameter of the circle = radius $\times$ 2

On substituting the values we get:

The diameter of the circle = 18 $\times$ 2 = 36 cm

Given that

The radius of a circle is a multiple of 3.

So, the radius of the circle can be 3$n$, where $n$ is any natural number.

Now, Diameter of a circle = radius $\times$ 2 = 3$n$ $\times$ 2 = 6 $\times n$

Hence, the diameter of the circle is a multiple of both 3 and 6.