Answers

2016-03-19T17:59:23+05:30
Even I want the same answer
0
yeah you are right answer is right. its a ratio so the both volume will have 3 in denominator, and finally they will cancel each other. so answer is 2:7.
thanks
wlcm
2016-03-19T18:35:23+05:30
Let a cone of radius r = 10 cm 
height = h cm

a/q,
volume of complete cone = πr²h/3
volume of part (i)  = π (r')² h/2
Volume of  part (ii) = total volume - Volume of  part(i)
                              = πr²h - π(r')² h/2
                              = πh{r² - (r')²/2}

Now,                            
l²  = r² + h²
⇒ r² = l² - h² -------------(1)

and 
(l/2)² = (r')² + (h/2)²
(r')² = (l/2)² - (h/2)² 
r ' =  \sqrt{(l/2 )^{2} - (h/2 )^{2} }  \\ r'= \sqrt{ \frac{ l^{2}- h^{2}  }{4}}  \\ r'= \frac{1}{2}  \sqrt{ l^{2}- h^{2}  }
r' = r/2
⇒ (r')² =  r²/4
Now, 
Volume of part (ii) = πh[r² - (r²/4)*(1/2)]
                              = πh(r² - r²/8)
                              = 7πhr²/8
And,
Volume of Part (i) = π(r/2)² h = πr²h/4
Ratio of volume of two parts = volume of part (i) ÷ volume of part (ii)
                                              =  πr²h/4 ÷  7πr²h/8
                                              = 2/7 =  2:7

0
answer is wrong i missed a denominator 3 of formula its pi r square h by 3.
bu t process is right
but on net the answer is 2:7
oops 1:7
hmmm solve it, then u will get the answer.