volume kerucut yang jari-jarinya 7 cm dan tinggi 21 cm

v = 1/3 phi r² t
v = 1/3 * 22/7 * 7² *21
v= 1078cm³

v. kerucut = 1/3×l.alas×t
= 1/3×(phi.r^2)×21
= 1/3×(22/7×7^2)×21
= 1/3×154×21
= 1078cm^3