If a man requires a mirror which is at least 0.9m long in order to be able to see his whole body when standing 2m away from the mirror. Calculate how long the mirror needs to be if he wants to see his whole body when he stands 6m away from the mirror

An interesting question - you can do the experiment yourself to see how distance from a mirror affects how much of your body you can see. But if you draw a sketch of the situation you should be able to figure this out pretty easily. Post back with what yuoou think the answer is and why, and we'll give you a hint if you still need it.