How do I do this?

Question

The 42km drive from Oakdale to Ridgemont usually takes 28 min. Because of highway construction requires a reduced speed limit, the trip now takes 14 min linger. Find the reduced speed limit in km

Answer 1

This one is far easier than it appears. The 42 Km distance hasn't changed, but the time has. Simply add the two times:

28min + 14 min = 42 min

The speed limit, which I assume you meant to write in Km / hr, would be calculated this way:

42 Km    =   1Km

 42 Min         1 min      We cancel the 42s to get this.

 

Since you want the time in hours instead, simply multiply by a conversion factor:

1 Km  * 60 min            We know minutes go on top because we want to cancel out the one on the bottom, and we also

1 mi      1 hour             know the hours must be on the bottom because that is how you write speeds. Cancelling the "min" 

                                   from both gives you:

60 Km

1 hour                         Also written as "60 Kph".