Final answer:
The next time the two radio stations will play the song at the same time is 72 minutes after they started playing at 3:00 PM; at 4:12 PM.
Step-by-step explanation:
To find the next time the two radio stations will play the song at the same time, we need to find the least common multiple (LCM) of 18 minutes and 24 minutes. The LCM is the smallest number that is divisible by both 18 and 24.
Prime factorizing the numbers, we have:
18 = 2 * 3 * 3
24 = 2 * 2 * 2 * 3
Now, we take the highest power of each prime factor:
2^3 * 3^2 = 72
Therefore, the two radio stations will play the song at the same time again after 72 minutes. Since they started playing at 3:00 PM, the next time they will play the song together is at 4:12 PM.