r=.... s=20 cm phi=22/7 luas selimut kerucut=880 cm2 luas permukaan kerucut=....

L selimut =πrs
880 =22/7 .r.20
6160 = 440 r
r = 6160/440
r= 14 cm

Lp kerucut = πr (r+s)
                  = 22/7.14 (14+20)
                  =44 (34) = 1496 cm²