Conversion of Units
How many feet are in 8 miles?
How many miles are in 3 kilometers?
To answer these questions and other similar conversion questions, we always set-up the problem
in the same way. We use multiplication and canceling.
Multiply ( what you want to covert ) by ( a conversion ratio ).
Cancel units.
Simplify the answer ( do the arithmetic ).
A conversion ratio looks very much like a fraction except that in the fraction there are units such
as miles, kilometers, inches, or centimeters too.
To correctly form the conversion ratio, the units of what you want to convert should be in the
bottom (denominator) of the fraction.
If you want to convert "miles" to "kilometers", when you form the conversion fraction the units
"miles" should be in the denominator of the fraction.
Example 1,
How many miles are in 3 kilometers?
Solution:
Multiply ( what you want to covert ) by ( a conversion ratio )
You want to convert 3 kilometers.
So you would write 3 kilometers where it says "what you want to convert" AND you would have
to form a conversion fraction with kilometers in the denominator.
Multiply ( 3 kilometers) by ( ? miles )
( ? kilometers) < notice kilometers on the bottom.
We get the information about miles to kilometers from a conversion table such as found at
http://startinbusiness.co.uk/si.htm
From the table we learn that 1 km = 0.621 miles,
so in the fraction replace the " ? miles " by " 0.621 miles " and the " ? kilometers " by " 1 km " .
