A simple pendulum swings with a period of 1.5 s. What would the period of the pendulum be if the length of its string were doubled, the mass of its bob were cut in half, and the force of gravity were doubled?

If you didn't know the formula for the relationship between the periodic time of a pedulum, it's length , mass of bob and force of gravity, here it is:

T=2\pi\sqrt{\frac{l}{g}}

T = Periodic time
l = length of string
g = acceleration due to gravity

Or, if you actually did the experiment, you'll see it immediately.

As you see in the formula, there is no mass. Therefore, the periodic time does not depend on the mass of the pendulum. Can you guess for the rest?