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Fun but hard math riddle.?
I got this riddle, if you know how to do it please can u show how.
" Assume that the Earth is a sphere, and a rope is wrapped all the way around the Equator, Another rope is wrapped around the Equator 2 feet above the ground directly over the first rope. The second rope is approximately how many feet longer that the first? "
3 Answers
- 1 decade agoFavorite Answer
Let R be the radius of the earth.
Length string 1 = Circumference earth = 2 (pi) R
Similarly,
Length string 2 = 2 (pi) (R + 2) = 2 pi R + 4 pi
length 2 - length 1 = (2 pi R + 4 pi) - 2 pi R = 4 pi
If we take pi to be about 3, this difference is about 4 (3) = 12 (feet)
Source(s): math major - 1 decade ago
The circumference of a circle is 2pi*r.
The radius of the inside rope is the radius of the earth R so its circumference is 2pi*R
The radius of the outside rope is the radius of the earth plus 2 so it's circumference is 2pi*(R+1)
To find how much longer it is plug in what the radius of the earth is and take the difference of the circumference:
2pi(R+1)-2pi*R
