InsatiaBull's amazing puzzle... How long's a piece of string?

Question

1. Wrap a piece of string around the diameter of a golf ball. Now you need to lift the string above the surface of the golf ball by a metre all round. How much extra string do you need?

2. Wrap a piece of string around the equator of the earth (assuming the string doesn't stretch, get wet and that the earth is smooth!). Now you need to lift the string above the surface of the earth by a metre all round. How much extra string do you need?

3. Subtract Answer 1 from Answer 2.

pitaguy2627 · Accepted Answer

circumference = diameter * pi
raising the string 1meter increase the diameter by 2 meters in both cases

so the answer for 1 and 2 is 6.28 meters of string
and 3 is 0.

Shy · Answer

Hi InsatiaBull

1.
let the radius of the golf ball be 'r' m's
String reqd for golf ball = 2Ïr
String reqd for 1 m above golf ball surface = 2Ï(r+1)

Extra string reqd = 2Ï(r+1) - 2Ïr = 2Ï


2.
Let the radius of the earth be R m's
String reqd for earth = 2ÏR
String reqd for 1 m above earth surface = 2Ï(R+1)

Extra string reqd = 2Ï(R+1) - 2ÏR = 2Ï


3. Difference between the two = 2Ï - 2Ï = 0

Trending News

InsatiaBull's amazing puzzle... How long's a piece of string?

2 Answers