If:

Computer A takes 4 hours to complete a set of operations,

and computer B takes 2 hours to complete the same set of operations,

how long does it take for both computers A and B working together to complete the same set of operations?

I'm having a hard time putting this into algebra. I arrived at numerous improper fractions and ultimately settled on "1 hour," but that doesn't seem right. Could somebody walk me through this?