Draw a ray diagra

(i)

(ii)

(iii)

Magnification = Height of Image/Height of Object

Sign Convention

(i) Distances measured perpendicular to and above the principal axis (along + y-axis) are taken as positive.

(ii) Distances measured perpendicular to and below the principal axis (along –y-axis) are taken as negative.

Magnification is positive for erect images and negative for inverted images.

Thus, magnification is positive in part (i) and (ii).

OR

(i) First we find the position of the image that will form

Using mirror formula,

so, we place screen at a distance 37.5 cm from the place, in front the mirror.

(ii) We know,

(iii)