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Distance, speed, time?
By James Smith on Thursday, August 09, 2001 - 12:42 pm:

HELP!
I'm trying to do problems using the distance=speed×time, speed=distance/time, time=distance/speed triangle and am getting confused. Especially with the time ones. i.e. TIME=7(miles)/40(mph). I get an answer of 0.175. Now is that .175 of an hour or 17mins 30 secs? How can I work these out?

By Susan Wakeling on Thursday, August 09, 2001 - 04:51 pm:

It is 0.175 of an hour. A nice way to work out what the units are is to do the sum with the units rather than the numbers and the answer you get is the units the answer is in. In this case mph=miles/hours, so unit of time=(miles)/(miles/hours)=hours. Does that make sense? Try it out with some others. This also explains why you shouldn't mix metric and imperial units because you would get a strange unit of time. Also, if the unit doesn't appear in the sum (minutes, in this case) then it doesn't appear in the answer. I hope that makes some sense....

By Arun Iyer on Thursday, August 09, 2001 - 07:08 pm:

Understanding units of measurement is by no means difficult.

Notably, arithmetic operations can be applied to these units.

e.g. 2 metres + 3 metres = (2+3)metres = 5 metres
6 metres/3 seconds = 2 metres/second

Another example is given by Susan.

Just remember that these units should be in the same system.

love arun

By Emma McCaughan on Thursday, August 30, 2001 - 04:37 pm:

If you want to turn 0.175 hours into minutes, then remember that
0.175 × 1 hour = 0.175 × 60 minutes