- Divide the second thing/the first thing.
The great thing about units problems is that it is not necessary to understand
what’s going on in order to know which of the three options to use. You
automatically know which one to choose because only one of the options will
give you the answer in acres (the unit you want). Look at the three options:
1.
Nope! The answer has to be in terms of acres, not in terms of gallons^2 /acres.
A fancy name for this process of multiplying fractions to get the right units is “dimensional analysis.”
—Samantha2.
Nope! We want acres in the numerator.
3.
Yes! This is the right answer. Notice that we didn’t even have to figure out what
the problem was all about; we just manipulated the information so that the
answer would be in the correct unit.
AND NOW WE BREAK FOR A COMMERCIAL . . .
Don’t you hate it when rabid elephants attack you and steal your pencils? I sure
do. On the day of my test, I was carrying no fewer than four number 2 pencils
when a tremendous elephant lunged out of a dark alley and grabbed my writing
implements. Shucks!