Let the diameter of the circle be x, that is, 3. 14X=( 15.7-X)×2, and the radius of X=6. 1 is 3.05.
Then calculate the semicircle area, that is, 3.14× 3.05× 3.05/2 =14.6.
The semicircle ocean circle surrounded by Uncle Zhang has a diameter below semicircle and a total length of15.7m.. This is my understanding.