Math CentralQuandaries & Queries


Question from Ariel, a student:

Mahtab took hours to drive from Mathville to Bioville, a total of 485 km. She drove part by highway at 80 km/h nd part by slow roads at 30 km/h. How many hours did she drive each type of road?

Hi Ariel,

You didn't say how many hours it took so I am going to say it took 7 hours for Mahtab to drive from Mathville to Bioville. Suppose she drove t hours on the highway then she drove 7 - t hours on the slow roads. You know that rate = distance/time so distance = time × rate. Thus on the highway she went a distance of t × 80 kilometres. How far did she go on the slow road? The sum of these two distances is 485 km. Solve for t.

I hope this helps,

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