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Craft teacher of a school taught the students to prepare cylindrical pen holders out of card board. In a class of strength 42,if each child prepared a pen

holder of radius 5cm and height 14cm, how much cardboard was consumed?

First we have to find the area of the circle and multiply its circumference by the height and add the both to get cardboard used for ONE pen holder. ∴(pi)(r²) =(22/7)(5) =110/7. Now its circumference=(pi)(d) =(22/7)(10) =220/7. It should be multiplied by height. ∴(220/7)(14) =3080/7 Now Adding (3080/7) + (110/7) =3190/7. now we have to multiply this by 42. ∴3190×42/7 =3190×6 =19140 cm ∴19140cm of cardboard was consumed.

No. of students = 42 Radius of holder = r = 5cm Height of holder = h = 14cm Now, Area of card board consumed = 42 x (curved surface area of cylinder + area of base) = 42 x (2 x x r x h + x = 42 x (2 x 22/7 x 5 x 14 + 22/7 x 5 x 5 = 42 x (2 x 22 x 5 x 2 + 22/7 x 5 x 5) = 42 x (440 + 550/7) = 42 x (440 x 7 +550)/7 = 6 x 3630 = 21780 ,, = Ans