Question

If the radius of the earth is 4000 miles, what is the length of its circumference?

Answer 1

Hint:To answer this question we will first know what circumference means. Later we will apply a simple formula that is the circumference of the circular (spherical) figure and find the circumference.

Formula Used:
\[C = 2R\pi \]
Where C = circumference and
R=radius.

Complete step-by-step solution:
Circumference is a curved geometric figure's enclosing boundary, especially a circle.
\[C = 2R\pi \]
It is given that
radius of the earth be 4000 miles
hence \[C = 2 \times 4000 \times \pi \]
\[ \Rightarrow C = 8000 \times \pi \]
\[ \Rightarrow C = 8000 \times 3.14\]
\[ \Rightarrow C = 25120miles\]
Hence the length of the circumference of earth’s surface with radius 4000 miles.
Additional Information:
The circumference of the Earth is the distance around it. It is 40,075.017 km around the Equator (24,901.461 mi). The circumference is 40,007,863 km when measured around the poles (24,859.734 mi). Since ancient times, measuring the circumference of the Earth has been important for navigation. In contemporary times, the circumference of the Earth has been utilised to define fundamental units of length measurement: the nautical mile in the seventeenth century and the metre in the eighteenth. The polar circumference of the Earth is quite close to 21,600 nautical miles since the nautical mile was designed to express one minute of latitude (see meridian arc), which is 21,600 partitions of the polar circumference.

 Note:1) Students should note that there is no different formula for circumference of circle and sphere, they are the same \[C = \pi r2\] and do not use the formula as \[C = \pi {r^2}\], it is wrong, it is the formula for area of the circle.