Several questions concerning age

[wang.cupid]

I know there are a host of ways to express people's age. for instance, the man aged 40, and etc. My question is, are the following expressions correct? I need to interchange them in my essay. thanks.

men aged 40-50
men at the age of 40-50
the 40-50-year-olds
those over 50s
those in the group over 50

Are there any other ways to express the same idea?

By the way, do I need of in the following sentence.

50% of students should do.........................

In this sentence, is or are is correct?
Half of them is/are doing .................

Many thanks.

[Tdol]

men at the age of 40-50
those over 50s- this could be right, but you might mean over 50
Also:

Men in their forties

[Rover_KE]

'...50% of students...' is correct.

'Half of them are doing....'

Rover