I have the question "If an object moving in a circle has a period of 24 hours, what is its frequency ?"
I know that frequency $= \frac{1}{T}$, where $T$ is the period.
Therefore, $f = \frac{1}{24}*60*60$ ( to get it in seconds)
And so the frequency is $150 Hz$.
Is this correct ?
Time period is $24 \textrm{ hours}$, it means: $$24\cdot 60\cdot 60 \textrm{ seconds}=86400 \textrm{ seconds}$$
Since you already know that:
$$\textrm{frequency} = 1/\textrm{time period}$$
$$\textrm{frequency}=\frac 1{86400}=1.15740740\times 10^{-5}\textrm{ Hz}$$
Always remember to use the data in appropriate units. If you will use the time period in hours, then you are not going to get frequency in Hertz.