You are driving home from school steadily at 90 km/h for 125 km. It then begins
to rain and you slow to 60 km/h. You arrive home after 2 hours and 30 minutes.
How far is your hometown from school?

Respuesta :

Answer:

  191 2/3 km

Explanation:

You want to know the distance traveled in 2 h 30 min if the first 125 km is traveled at 90 km/h and the remainder is traveled at 60 km/h.

Time

The relation between speed, distance, and time is ...

  t = d/s

Here the total time will be the sum of the times of the two legs of the trip. In hours, that is ...

  2.5 = 125/90 +(d -125)/60 . . . . . . . where d is the total length of the trip

Solution

  2.5 -125/90 +125/60 = d/60 . . . . . . add the opposite of non-d terms

  d = 60(2.5 +125(1/60 -1/90)) . . . . . . multiply by 60

  = 60(2.5 +125/180) = 191 2/3

Your hometown is 191 2/3 km from school.

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Additional comment

You drove 1 h 23 min 20 s at speed, and 1 h 6 min 40 s in the rain.