Mr. Ohashi's Math Homepage

CONVERTING UNITS

Understanding how to convert the units of rates is a difficult, but important skill. Listed below are the steps that we learned in class.

Suppose we wanted to solve the following problem: 40 feet per second is how many miles per hour?

Step 1: Understand the problem
We first need to figure out what units we are starting with and what units we want to end up with.
In this case, we are starting with feet per second and want to end up with miles per hour

Step 2: Figure out what conversions you need to do
Next we need to figure out what units we will have to go through to complete the conversion.
In this case, we will have to convert...

Step 3: Find your conversion factors
Now find the conversion factors for each conversion that we have to do.

Step 4: Set up the math problem
Next comes the math. Start with what you were given and multiply it by the conversion factors. Make sure to match up diagonally the units you don't (if one is on the top of a fraction, then another goes on the bottom). These will cancel out later.

Step 5: Cancel out the units
Now you can cancel the units that have one on top and one on the bottom. If you did Step 4 correctly, you should be left with just the units that you wanted.
Notice how in our example, the only units left are miles (on top) and hours (on bottom). This gives us miles per hour!

Step 6: Multiply and solve
Now multiply the top numbers to get our answer's top number. Then multiply the bottom numbers to get our answer's bottom number. Divide the top and bottom to get one final answer. Now you are done!