- Thread starter speedy
- Start date

- Joined
- Nov 12, 2017

- Messages
- 8,887

Since Earth is not a perfect sphere of 4000 miles radius, I could logically say anything I want and my statement would be "true"; but that wouldn't be what you're asking. You mean, "If Earth *were *a perfect sphere of 4,000 miles radius what would be its circumference in miles?"

Do you know the formula for the circumference of a circle? It's \(\displaystyle C = 2\pi r\).

Replace \(\displaystyle r\) with 4000, and do the calculation.

Do you know the formula for the circumference of a circle? It's \(\displaystyle C = 2\pi r\).

Replace \(\displaystyle r\) with 4000, and do the calculation.

Last edited by a moderator:

- Joined
- Jun 18, 2007

- Messages
- 22,160

Circumference of a sphere is defined as the circumference of the great circle around the sphereIf Earth is a perfect sphere of 4,000 miles radius what is it's circumference in miles?

Circumference C = 2 * \(\displaystyle \pi \) * radius

Continue....

Have i worked it out correct = 25132.74 milesSince Earth is not a perfect sphere of 4000 miles radius, I could logically say anything I want and my statement would be "true"; but that wouldn't be what you're asking. You mean, "If Earthwerea perfect sphere of 4,000 miles radius what would be its circumference in miles?"

Do you know the formula for the circumference of a circle? It's \(\displaystyle C = 2\pi r\).

Replace \(\displaystyle r\) with 4000, and do the calculation.

- Joined
- Dec 30, 2014

- Messages
- 8,085

I don't know as you never said what the circumference equals. Please give complete answers.Have i worked it out correct = 25132.74 miles

Yes, 25132.74 is the correct answer to 2 decimal places for the calculation 2*pi*4000 (in miles)Have i worked it out correct = 25132.74 miles

- Joined
- Jan 7, 2020

- Messages
- 25

Here r= 4000 miles,

Circumference= 25132.74 miles

Above mentioned answers are correct.