http://s3.supload.com/free/conversion_p ... .jpg/view/
the link shows the work for using CONVERSION FACTORS to accomplish this conversion.
here are the basics of the process:
* start with the
starting information, usually a concrete value. here, that concrete value is 22 yards.
note that
rates are not "starting information"; those count as conversion factors.
* to accomplish the conversion, create CONVERSION FACTORS, which have EQUAL quantities on the top and bottom of the factor. there are two types of such conversion factors:
- RATES (which are naturally fractions already)
- REFERENCE CONVERSIONS (such as 12 inches = 1 foot) which are universally true and could be looked up in a reference book if necessary.
* position the fractions so that UNWANTED UNITS CANCEL and the desired units are left in the desired places.
- note how the 45 mph is positioned so that it's 1 hour per 45 miles, not 45 miles per 1 hour. this is done so that the miles are cancelled out.
--
in the problem shown, 22/1760 cancels down to 1/80, and 3600/45 cancels down to 80/1. therefore, 80/80 = 1, so the whole fraction gives
1 second. are you sure you didn't copy some number with an incorrect decimal place or other similar error?
plus, think about this intuitively: if a car is traveling at 45 miles per hour, which is approaching highway speeds, then it's ridiculous to think that it would take 8 to 12 seconds to travel 22 yards. the average human can
run 22 yards in about three seconds. check the problem!