A pendulum oscillates 40 times in 4 second.find it's time period and frequency?

This is awfully basic information. You need to study your book and learn what the words mean.

frequency is the number of oscillations per second (or other time period).
40/4 = 10 cycles per second = 10 hertz

period is the time of one oscillation
4/40 = 1/10 second