Question

An object is placed exactly between a convex and concave mirror each of focal length 15 CM

Answer 1

Here is your answer

since in case of spherical mirrors, the focal length is half of radius of curvature, so the object is at the radius of curvature of mirrors.

thus the cnvex mirror will form a virtual image of the object at the distance of radius of curvature of mirror behind the mirror.

SO and in the other case, the image is formed just below the object itself due to the concave mirror.