What's the answer? Course it's good to start out misspelling puzzle.... sheesh... I came up with 62.265cm... This 'Simple' Puzzle Once Stumped 96% of America's Top Math Students
I say 20 cm. My explanation below. Skip past this if you still want to work it out yourself. First, reduce the problem. The string goes around the circumference 4 times on a 12 cm length tube (rod). That's the same as 1 time around a 3 cm length tube, and multiply by 4 for the final answer. So we start with a tube of 4 cm circumference and 3 cm length, and the string goes around it once. Now imagine that we cut the tube lengthwise between where the string begins and ends. Unroll the tube. You will get a rectangle of 3 cm (tube length) x 4 cm (tube circumference) On this rectangle, the path of the string going around the tube 1 time is from one corner to the opposite corner. The string is the hypotenuse of a right triangle with 3 x 4 sides. Applying the Pythagorean theorem, the hypotenuse (string length) is 5. Multiply by 4 to get the final result 20.
Krikey... I misread the circumference for the diameter... It pays to read the instructions first... It's a 3,4,5 triangle as you pointed out...
I think the puzzle that stumped 96% of the math people was the birthday on mentioned in the article not the pipe. I followed their link to it. Can You Solve the Math Problem That Has Torn Singapore Apart?
But for 4 cm diameter, I get 51.678. 4 * sqrt( (4 * pi)**2 + 3**2 ) As the problem said, "Show your work".
My reasoning was the string had to do two things... Go around the rod 4 times and reach to the end of the rod Pi x D =12.566 x 4 of them = 50.265 + 12 (length of rod) = 62.265cm But my reasoning was flawed...
The length of the string is the length of the diagonal of the rectangle with l = 4 \cdot 4 cm = 16 cm\ and\ w = 12 cm Therefore the length of the string is s = \sqrt{16^2 + 12^2} = 20\ cm
Gave the same quiz to my daughter... She processed the answer the same as what you used and told me the answer was 20cm....