Every 10 seconds a pendulum completes 2 cycles. what are the period and frequency of this pendulum?

(10 seconds) / (2 cycles)

= (10 / 2) seconds/cycle

= 5 seconds/cycle.

That's the period of the pendulum's swing.

The frequency is just the reciprocal of the period ... 1 over it.

1 / (5 seconds per cycle)

= 5 cycles/second (5 Hz)