If a cone is cut into two parts by a horizontal plane passing through the mid points of its axis,then what is the ratio of the volumes of upper and lower part?

If we cut cone from midpoint then
use similarly concept.
let r is radius of above part and R is the radius of base of cone.
R/r=h/(h/2)=2/1
R=2r
now 
volume of cone =πR²h
=π(2r)²h=4πr²h volume of small cone =πr²h/2
now,
volume of below part =4πr²h-πr²h/2
=7/2 πr²h 
now ratio = volume of above part/volume of below part
=(πr²h/2)/(7/2πr²h)=1/7
hence ratio =1:7