In the previous reading, we talked about how to do simple unit conversions - things like converting meters to kilometers, feet to inches, and days to weeks. Sometimes, though, you may face situations where you don't know the conversion factor. For example, suppose someone asked you to convert 2 days to seconds. Do you know, off the top of your head, the conversion factor from days to seconds? 

I don't.

So what do we do? We do the conversion in stages, like this:

(2 days) x (24 hours)/(1 day) = 48 hours
(48 hours) x (60 minutes)/(1 hour) = 2,880 minutes
(2,880 minutes) x (60 seconds)/(1 minute) = 172,800 seconds

You see what I did, right? I first converted days to hours, then converted hours to minutes, then converted minutes to seconds. Of course, I could have done the whole thing in one line:

(2 days) x (24 hours)/(1 day) x (60 minutes)/(1 hour) x (60 seconds)/(1 minute)

As you multiply all those fractions across, you'll notice that the numerator of one fraction will cancel with the denominator of the next, so when you're all done, you'll just have a unit of seconds, which is what you're supposed to have.

Example Two - Convert 12 yards to inches by daisy chaining conversion factors.

Answer - Our conversion factors are (3 feet)/(1 yard) and (12 inches)/(1 foot).

(12 yards) x (3 feet)/(1 yard) x (12 inches)/1 foot) = 432 inches.