Diketahui: Diameter dan tingggi tabung = diameter bola luas selimut = 80cm² Berapakah luas permukaan bola?

Ls= 4 x phi x r²                                                                                                                 80 = 4 x 3,14 x r²                                                                                                              80 = 4 x 3,14 x r²                                                                                                                                           80 = 12,56 x r²                                                                                                                         = 80 : 12,56= √6,4= 2,5                                                                                                      Lp= 4 x phi x r²                                                                                                                     Lp= 4 x 3,14 x 2,5 x 2,5 = 78,5 cm²