Math CentralQuandaries & Queries


Question from Diana, a student:

if a car travels 30.0 km per hour, how many km will it go in 2.0
hours? How far will it go in 15 minutes?

Hello Diana,

You can think of 30km/hr as saying that 30km is equal to 1 hour.
i.e. 30km = 1hour
(Technically this makes no sense at all physically, but this is how we interpret the situation)
So, 2hours = 2(30km) = 60km. Hence, the car goes 60km in 2 hours.

This works if the units match, so to find out how far the car travels in 15 minutes, we need to convert to hours. 15 minutes is how much of an hour? Proceed as before to determine how many kilometers.


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