A roll of material with dimensions 25m long and 150cm wide is given to make 600 cylindrical pencil cases calculate using A=LxB

Question

Height =178mm Diameter =95mm. Surface area = 2xarea of bade+perimeter of base x height of pencil case

Answer 1

25m=2500cm. Area of pencil case=2(πr^2) [top and bottom surfaces]+2πrh [curved surface of the cylinder], where h=17.8cm, r=9.5/2=4.75cm. Total SA of case=2πr(r+h)=2π(4.75)(4.75+17.8)=9.5π(22.55) sq cm.

600 cases have a total SA of 5700π(22.55) sq cm = 128535π sq cm = 403805 sq cm approx.

Area of sheet=2500*150=375000 sq cm, which does not cover the required surface area.

The deficiency is 28805 sq cm (at least).