Choose and EXPLAIN your answer:-
Hiralal has two wooden cubes of side 'a' cm each. He carves one of them into the LARGEST POSSIBLE CYLINDER and fixes the two solids together as shown below.
He now wants to cover this solid
entirely with a coat of paint.
Assuming pi = 3, the total area to
be painted (in cm2) will be close to
A) 8.75a2
B) 9a2
C) 10. 5a2
D) 12a
Answers
Given : Hiralal has two wooden cubes of side 'a' cm each. He carves one of them into the LARGEST POSSIBLE CYLINDER and fixes the two solids together
pi = 3
To Find : total area to be painted (in cm²) will be close to
Solution:
By seeing picture carefully we can conclude that surface area to be painted
= Surface area of Cube + Curved surface area of cylinder
As top surface of cylinder area = bottom surface which reduce the surface area of cube
Surface Area of Cube = 6a² cm²
Diamter of cylinder = a cm => radius r = a/2 cm
Height h = a cm
Curved surface area of cylinder =2πrh
= 2π(a/2) a
= πa²
π = 3
= 3a² cm²
Total area to be painted (in cm²) = 6a² + 3a² = 9a²
9a² is the correct option
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