Let h2 be the height of image and h1 be the hight of object
as condition h2/h1=2
As magnification m=h2/h1=v/u
as v=100 cm,,as object placed at right side then u always negative
by lens formula
power =100/f=3D
object should place at 50cm from pole of lens
Sorry for ray diagram,It is typical to draw on this page 
2 4 2
is there any need of improvement in this answer
could u tell where the objct should b placed whether on F or P or C.....
how did u get 50
as mention v=2u, we have given v=100cm then simply we find u
as f=33.3 then c=2f=66.6 as u=50cm.From all this we conclude that object is placed between f and C