Homework Help: Maths

Posted by Sindy on Wednesday, April 21, 2010 at 8:57am.

Any help with the following would be greatly appreciated. I don't understand how to use the information given to create the equation.

1) A car travels between A and B at an average speed of 60 km/h. If the car increased its
average speed to 100 km/h it would take 10 minutes less to make the trip. How far is it
between the towns?

2) Car A is travelling along a freeway at 100 km/h when it is passed by car B. If both cars
maintain a constant speed and the end of the freeway is 10 km away, find the speed at
which car B must travel to beat car A to the end of the freeway by 1 minute.

Maths - bobpursley, Wednesday, April 21, 2010 at 9:46am
1) You start with the definition of average speed.

avg speed= distance/time
60km/hr= 1km/min= distanceab/time

distanceab= 1km/min*time
but also
distanceab= 100km/60min*(time-10)
set these two equations equal, solve for time, then, find distance from the original equation.

2) distance= speed*time
10km= 100km60min*time
10km= speedB*(time-1)
again, set them equal, solve for time, then solve speedB

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