A bus travels 20 km in 30 minutes. What is the average speed of the bus?

The answer is 40 km/h but how do I figure that out?

20 / 0.5 = 40

30 minutes is 0.5 as a decimal. You then do Distance / Time to get your answer.

20/30 = x / 60 ... 20 km to 30 min = x km to 60 min (because there is 60 minutes in an hr)

u will then cross multiply because this is a proportion

(30) (x) = (20) (60)

30x = 1200

x = 1200/30

x = 40 ... so 20 km in 30 min = 40 km in 60 min (per hr)