Here R=16 cm , r=10 cm and h=21 cm
volume of frustum of a cone `=(pih)/(3)(R^(2)+r^(2)+Rr)`
`=(22)/(7)xx(1)/(3)xx21(16^(2)+10^(2)xx10)`
`=22xx516xx=11352 cm^(3) =(11352)/(1000)`litres=11.352 litres
Now for slant height l of furstum
`l^(2)=h^(2)+(R-r)^(2)`
`l^(2)=21^(2)+(16-10)^(2)`
`l^(2)=441+36`
`l^(2)=447`
`l=sqrt(447)`=21.84 cm
Now S.A of bucket =`pirl(R+r)+pir^(2)`
`=(22)/(7)xx21.84xx(16+10)+(22)/(7)xx10^(2)`
`=(22)/(7)(21.84xx26+100)`
`=(22)/(7)xx667.84=2098.9+2 cm^(2)=20.99 dm^(2)`
Cost of sheet @ 1.50 per sq dm.
=`20.99xx1.50` =Rs 31.49