a train runs at 72 km/h. what is the speed in m/min?
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Answer:
A conversion factor is a fraction equal to 1. You are given that one hour equals 60 minutes so you can write that as hr/60min=1 or 60min/hr=1 whichever works for you and drop it into an equation anywhere and it only changes the units.
ANSWER = You write this first so it looks like you know what you are doing. That gives you a bit of time to figure out what to do next.
ANSWER = 72 km/h x 1000m/km x 60min/h x 60sec/min
Ok, now we check everything. This is called sanity check and it is especially important in chemistry and physics where you might have a dozen or so conversions in a single equation. We have km above the line and again below. We have h above … oops, the h does not cancel.
ANSWER = 72 km/h x 1000m/km x h/60min x min/60sec
When you are sure everything is right, multiply all the numbers above the line and divide by all the numbers below the line.
ANSWER = 20 m/sec