Since the half-life of sodium-24 is 15 hours, it means that after every 15 hours, the activity of the sample will decrease by half.
After 45 hours, which is three times the half-life, the activity will decrease by a factor of 2^3 (2 raised to the power of 3), which is 8.
So, to find the activity after 45 hours, we can take the original activity of 500 Bq and divide it by 8.
500 Bq divided by 8 is 62.5 Bq.
Therefore, the activity of the sample of sodium-24 after 45 hours would be approximately 62.5 Bq.
