Q56 of 56 Page 13

The diameters of the lower and upper ends of a bucket in the form of a frustum of a cone are 10 cm and 30 cm respectively. If its height is 24 cm, find :

(i) The area of the metal sheet used to make the bucket.


(ii) Why should we avoid the bucket made by ordinary plastic? [Use π = 3.14](CBSE 2018)


(i) Given: R = 15cm; r = 5cm; h = 24cm


Curved Surface Area of Frustum


Where, R = Larger radius of the frustum


r = Smaller radius of the frustum


h = Height of the frustum


CSA of the frustum



Area of the base of the bucket = Area of circle


where “r” is the radius of circle


= π(5)2 = 78.5sq.cm


So, total area pf the bucket = CSA of the frustum + Area of the circle


= 1632.8 + 78.5 = 1711.3 sq. cm


1711.3 sq. cm of metal sheet is required to make the bucket.


(ii) We should use biodegradable materials for the bucket which can be decomposed by the natural processes of the environment. Ordinary plastic is not biodegradable and can cause soil pollution. It can also harm animals if consumed.

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