Jawapan

2016-10-01T19:40:10+08:00
2πj² = 18.65
j² = 18.65 ÷ 2π
j²= 2.97
j = 1.7 cm
2016-10-01T19:40:27+08:00
1/2 x 4/3 pi r^3 = 18.65

r = 2.07 cm