# Chemistry

The speed limit on a certain highway is 72km/h. What is the speed in cm/s?

Could you go through each step on how to get the answer? Lots of the questions are like this one, but I don't know how to do them.

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1. if something is the same top and bottom, I call it one.
for example
100 cm / 1 meter = 1 in my world, but the units change without changing the value
so

72 km /h (1000 m/1km)(100 cm/m)(1h/3600s)

km cancels
h cancels
m cancels
and I am left with cm/s
now do the calculation
2000 cm/s

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2. could you go through the steps in a different way maybe? I still don't get it.

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3. by the way, I use it so much that I remember 3600 s/h
but

(60 min/h)(60 s/min)

min cancels and I have (3600 s/h)

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4. Oh! Ok, thank you! I get it know.

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5. well you can do it in what I think are much more difficult ways
Like say I need to go from km to cm
well a km is 1000 meters and a meter is 100 cm so a km is 100,000 cm
so multiply your
72 km/h by 100,000 to get 7,200,000 cm/h
now deal with the hours
1 hour = 60 min and each min is 60 seconds so
1 hour = 3600 s
so divide 7,200,000 cm/h by 3600s/h
to get
2000 cm/s

If you need to do a lot of these, it is a lot easier to do it my way :)

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6. I did have a lot of those questions and I used the method you did. Thanks for the help!!!!!

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7. Great, good luck !

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