Surface Area of Composite Figures


 
 
Concept Explanation
 

Surface Area of Composite Figures

Surface area of Composite Figures:

Example: A solid wooden toy is in the shape of a right circular cone mounted on a hemisphere. If the radius of the hemisphere is 4.2 cm and the total height of the toy is 10.2 cm, find the volume of the wooden toy.

Solution: Let r be the radius of the hemisphere and h be the height of the conical part of the toy. Then, r  = 4.2 cm, height of cone = (10.2 - 4.2) cm = 6 cm. Also, radius of the base of the cone = 4.2 cm

large therefore    Surface Area of Composite Figure = CSA of cone + CSA of hemisphere =   = large frac{pi r^{2}}{3}(h + 2r)cm^{3}

= large frac{1}{3}times frac{22}{7}times 4.2times 4.2 times (6+2times 4.2)cm^{3}

= large frac{1}{3}times frac{22}{7}times 4.2times 4.2 times 14.4 cm^{2} =266.11 cm^{3}

Composite Figures

A figure (or shape) that can be divided into more than one of the basic figures is said to be a composite figure (or shape).

For example, figure ABCD is a composite figure as it consists of two basic figures.  That is, a figure is formed by a rectangle and triangle as shown below.

The area of a composite figure is calculated by dividing the composite figure into basic figures and then using the relevant area formula for each basic figure.

Example:- Find the area of the following composite figure:

Solution:

The figure can be divided into a rectangle and triangle as shown below.

So, the area of the composite figure is 216 cm2.

 

Sample Questions
(More Questions for each concept available in Login)
Question : 1

A storage tank consists of a circular cylinder, with a hemisphere adjoined on either end. If the external diameter of the cylinder be 1.4 m and its length be 5m, what will be the cost of painting it on the outside at the rate of Rs 10 per square meter?

Right Option : A
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Explanation
Question : 2

A storage tank consists of circular cylinder with a hemisphere adjoining at either end. If the diameter of the cylinder be 1.4 m and its length be 8 m, the cost of painting it on the outside at the rate of Rs 10 per m2 will be _______________

Right Option : A
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Explanation
Question : 3

A cylinder is of height 31 cm and base radius 7 cm. A hemisphere of radius equal to base radius of cylinder is cut off from one end radius of cylinder is cut off from one end a cone of maximum height from remaining part is also cut off. The curved surface area of the remaining part is ______________

Right Option : A
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Explanation
 
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