A concave mirror having the focal length 15 cm, forms an image having twice of the linear dimensions of the object. If the image is virtual, then the position of the object will be

Image formation by concave mirror will be as follows:Given,  m=image  distanceobject  distance=−vu=2⇒v=−2uAlso  1f=1v+1uWhere  f  is  focal  length,  v  is  image  distance  and  u  is  object  distance.⇒−115=1u−12u=12u⇒u=−152=−7.5  cmThus,  the  object  should  be  placed  at  a  distance  7.5 cm  in  front  of  the  mirror.