Question

Find the ratio 30 days to 36 hours.

But for this, both the quantities should have the same units. So, first we convert days into hours and then calculate their ratio. To convert days into hours, multiply the number of days to 24 (Since, 1 day has 24 hours). Hence, 30 days $= 30 \times 24 = 720$ hours.
The ratio of 30 days to 36 hours = $720:36$
The ratio of 30 days to 36 hours = $20:1$