19 hours to 72 days is 19:72 as a ratio and 19/72 as a fraction.

Now, we have to find a common factor between 19 and 72, however 19 is a prime number meaning that is

Now, we have to find a common factor between 19 and 72, however 19 is a prime number meaning that is

**only**divisible by itself and one. But, dividing by one will only give us the same ratio.Hence, 19:72 is a ratio already expressed in its lowest terms.