Radius is Half the Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle. The word "diameter" derives from Greek (diametros), "diagonal of a circle", from (dia-), "across, through" + (metron), "a measure. (Source wikipedia)



Radius is defined as the half of the diameter .we can write

Radius = half of the diameter or `(diameter) / 2`

Here we are going to study about how to solve the diameter problems and its example.

Radius is Half the Diameter – Example Problems:

Example: 1

Calculate the area of the circle with diameter of the circle is 39 meter.

Solution:

We know the formula for calculate the area of the circle = `pi ` r2

In this problem diameter is given so we have to find the radius we know the radius is half of the diameter so we have to divided by two

Radius = `(diameter) / (2)`

r = `39/2`

r = 19.5 meter

Now we find the area of the circle

Area = 3.14 * 19.52

Area = 3.14 *19.5 * 19.5

Simplify the above we get

Area = 854.86 meter square

Therefore the area of the circle is 1193.98 meter2


Radius is Half the Diameter – Example: 2

Find the surface area of the sphere with diameter is 23 cm

Solution:

We know that formula for finding surface are a of the sphere = 4 `pi` r2

In this problem diameter is given so we have to find the radius we know the radius is half of the diameter so we have to divided by two

Radius = `23 /2`

r = 11.5 meter

Now we find the surface area of the sphere

Area = 4 *3.14*11.52

Area = 4 *3.14*11.5*11.5

Simplify the above we get

Area = 1161.06 meter square

Therefore the surface area of the sphere = 1161.06 meter2