After some practice, multiplying and dividing units will be as simple and as
natural to you as multiplying and dividing numbers.
We will now do a practice problem from a real SAT that shows the procedure
for solving units problems.
A gasoline tank on a certain tractor holds 16 gallons. If the tractor
requires 7 gallons to plow 3 acres, how many acres can the tractor
plow with a tankful of gasoline?A) B) C) D) There are two steps to all units problems:- Figure out what information is given.
- Pick, from only three options, what to do with that information in order
to get the correct unit in the answer.
Quick tip: If you multiply the plow something close to 6 acres^7 / 3 gallons/acres ratio by 2, you find that it takes 14 gallons to plow 6 acres. Now you know 16 gallons will.
—Samantha
Step 1: Figure out the information given.
a. “7 gallons to plow 3 acres” = 7 gallons/3 acres
b. “A gasoline tank holds 16 gallons” = 16 gallons
c. “How many acres?” means . . . answer in acres.Step 2: Do the right thing with the information given.
In all units problems, you have three options for what to do with the given
information:
- Multiply the first thing × the second thing.
- Divide the first thing/the second thing.