There is such a math problem in ancient mathematics in China: There is a tree standing upright on the ground, 2 feet high and 3 feet thick. There is a vine winding from the root and reaching the top of the tree for 7 weeks. How long is this vine? (Note: Dead trees can be regarded as cylinders; The tree is 3 feet thick, which means that the circumference of the cylindrical part is 3 feet. 1 ft =1ft)

This problem needs us to solve.

There are 7 stay cable lengths in total. The length of each stay cable can be calculated by Pythagoras' law. The length is 3 feet and the height is 2 feet, that is, 20 feet. Divided by 7 equals 20/7 feet.

Let the cable-stayed length be d: (20/7) 2+3 2 = d2.

D=29/7

Then the total length of the stay cable is 6×D=6×29/7=29 feet, which is 2 feet 9 feet long.

So the total length of the vine is 2 feet 9 feet.