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Time, Speed, Distance, and Unit Conversion

Date: 7/30/96 at 11:46:41
From: Anonymous
Subject: Time, Speed, Distance, and Unit Conversion

If you were traveling in a car moving at a constant velocity of 44 mph 
for 50 minutes, how many kilometers would you have travelled?



Date: 7/30/96 at 13:7:19
From: Doctor Paul
Subject: Re: Time, Speed, Distance, and Unit Conversion

We begin by converting mph to kph and minutes to hours:

44 miles     5280 feet      12 inches     2.54 cm    1 meter   1 km
-------  x  ------------ x  ---------- x  ------- x -------- x -----
  hour        1 miles        1 foot       1 inch     100 cm    1000 m

Note that all I am really doing is multiplying by one.  5280 feet and 
1 mile are equivalent.  Also note that all of the units will cancel 
except km / hr

multiply it out:

44 mph = 70.81 kph

50 minutes       1 hour
----------- x  ----------
    1            60 minutes

multiply it out:

50 minutes = .83 hrs

So we move 70.81 kilometers      .83 hours
           ----------------  x   -----------  = 
               1 hour               1

multiply it out, solve, cancel out the hour unit and you get

58.77 kilometers.

-Doctor Paul,  The Math Forum
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Associated Topics:
Middle School Ratio and Proportion
Middle School Terms/Units of Measurement

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