Given:R=3cm, H=10.5cm⇒Surface area = Curved Surface Area + Base Area=2πrh+πr2=2×722​×3×1010.5​+722​×3×3cm2=198+7198​cm2=71584​cm2⇒Area of cardboard sheet used by competitor =71584​cm2⇒Area of cardboard sheet used by 35 competitors =71584​×35=7920cm2