Question

How many swings would a 23 cm long pendulum make in 30 seconds?

Answer 1

Is there any possible chance that at some point in your science
studies, sometime before you were given this question for your
homework, that maybe you might have encountered this formula
for the period of a simple pendulum ?

                   Period = (2 pi) √(length/gravity) .

If the length is 0.23 meter, and the
acceleration of gravity is 9.8 m/s²,
then the period is

                                 = (2 pi) √(0.23/9.8)

                                 =   0.963... second  (rounded)

That's how long it takes for a simple pendulum, 23cm long,
hanging on a massless string and not swinging too far to
the side, to complete one full swing left and right.

Now, if you can figure out how many periods of  0.963 second
there are in  30 seconds, you'll have your answer.  I'll leave
that part of it to you.