Question

A man stands 10 m in front of a large plane mirror. How far must the walk before he is 5 m away from his image?

Answer 1

Man should walk 7.5 m towards the mirror.
The reason being, the image formed by a plane mirror is the same distance behind the mirror as it is between the object and the mirror. A distance of 5m between man and his image means that the distance between him and the mirror = `52`= 2.5 m.
Thus, the distance he should walk = 10 - 2.5 = 7.5 m.