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ankit kumar

· started a discussion

· 1 Months ago

q (Question: 186239.0 )

answer is wrong. cone is cut from solid sphere then why we take hemi shere. please clarify it. or it's a fault of language...................................................

Question:
A solid cone of height 9 cm, with diameter of its base 18 cm, is cut out from a wooden solid sphere of radius 9 cm. The percentage of wood wasted is –
Options:
A) 25
B) 30
C) 50
D) 75
Solution:

Hieght of cone is 9cm

radius of cone is 9cm

therefore volume of cone will be=1/3πr²h

                                             =πx3 x 9 x 9

                                             =243π

now volume of sphere is =4/3πr³

                                    =4/3*π*9 x 9 x 9=972π

therefore volume of wood left=972π-243π=729π

therefore percentage of wood waste=729π/972π x 100

                                                   =75% 

Knowledge Expert

· commented

· 1 Months ago

75% is correct, we found an error in the solution, we fixed it....Thanks for noticing.......
Hieght of cone is 9cm
radius of cone is 9cm
therefore volume of cone will be=1/3πr²h
=πx3 x 9 x 9
=243π
now volume of sphere is =4/3πr³
=4/3*π*9 x 9 x 9=972π
therefore volume of wood left=972π-243π=729π
therefore percentage of wood waste=729π/972π x 100
=75%

Ankur Bhatia

· commented

· 1 Months ago

your answer is correct this expert is wrong here

Knowledge Expert

· commented

· 1 Months ago

@durgesh gupta Exactly :)

durgesh gupta

· commented

· 1 Months ago

its looking like that, but answer is correct....
b/o the radius of both sphere and cone are same, so a largest cone will be formed of same radius as that of sphere(now hemisphere. the base of cone will be same as the diameter of sphere.

Talented Boy

· commented

· 1 Months ago

50% is the correct answer....

Please read the question very carefully, solid cone is cut out from a wooden solid sphere, now its hemisphere....

so, apply formula, volume of hemisphere...Thats it.......
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