Question
Tue November 22, 2011 By: Aviral Raj

sir can you please explain the following ques. in the lesson I was unable to understand it. The question is If the radius and height of a cylinder are in ratio 2:7 and its volume is 704cm, then h of the cylinder is ?

Expert Reply
Wed November 23, 2011
Explanation of the Question--
 
the first line of the question says that radius and height of the cylinder are in ratio 2:7
this means that if you divide the radius by height then you will get the ratio equal to
2:7. Let us say the radius is r and height is h
 
Then it means r/h = 2/7. Or it also means that if you let r=2x then the height will be 7x
 
second part of the question says that the volume of the cylinder is 704cc
this is a simple statement telling the volume of the cylinder
 
now the question asks you for the height of the cylinder. it has given you two information
one with the ratio and other with the volume , you now need to find the height.
 
SOLUTION --
 
Let us say radius is r and height is h
 
then r/h = 2/7
 
or, r=2h/7
 
Now volume of cylinder = ?r2h= 704
 
put the values we get
 
(22/7)x(2h/7)2h= 704
 
h3 = 704x73/22x4
 
h3 = 8x73
 
h3 = 23x73
 
so, h = 14
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