hitung luas bola jika luas selimut tabung 2.464 cm persegi dan phi =22/7

Lselimut = 2 × phi × r × t
2464 = 2 × 22/7 × r × 2r
1232 = 22/7 × r × 2r
r × 2r = 1232 × 7/22
r × 2r= 8624/22
2r^2 = 392
r^2 = 196
r = 14

Lbola = 4 × phi × r^2
L = 4 × 22/7 × 14 × 14
L = 88 × 2 × 14
L = 88 × 28
L = 2464 cm^2