Question

$\huge \fbox \red{❥ Question}$


Rasheed got a playing top (lattu) as his birthday present, which surprisingly had no colour on it. He wanted to colour it with his crayons. The top is shaped like a cone surmounted by a hemisphere. The entire top is 5 cm in height, and the diameter of the top is 3.5 cm. Find the area he has to colour. (Take π = 22/7)



(REQUIRED QUALITY ANSWER)

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Answer 1

T.S.A. of top= C.S.A of hemisphere +CSA of Cone

Now,the CSA of hemisphere

= 1/2•(4πr²)=2πr²

= [2•22/7•(3.5/2)²]

Also,

the height of the cone= height of top - height(radius)of the hemispherical part

=(5+3.5/2)cm= 3.25cm

So, the slant height of cone(l)

= √r²+h²

=√[(3.5/2)²+3.25]cm

=3.7cm(approx)

Therefore,CSA of cone

= πrl=[22/7•(3.5)•3.7]cm²

This gives the surface area of the top as

= [2x22/7x (3.5)²]cm²+[22/7x3.5/7x3.7]

=22/7x3.5(3.5+3.7)cm²

=11/2x(3.5+3.7)cm2=39.6cm²..ans