Question

what is the answer of no. 21? How?

Answer 1

5m becoz distance b/w u and mirror is 2.5m and sm frim mirror to image so 5m

Answer 2

when the girl is 2m away from the mirror her image will be formed 4m away. If she moves away from the mirror by 0.5m her image will also move away from the girl by 0.5 m
Therefore distance between girl(object) and image is 4+0.5+0.5=5m