How many cubs can a panda have at once and how long does it take for a mother panda to give birth?

This is a question for school.

I believe that pandas can only have 1 cub at a time. (Online it says 1.5 cubs but I’m not quite sure how half a cub would work) Their gestation period (how long it takes them to have their cub) is 3-5 months. This is for a giant panda.