EXAMPLE 1

Let's look at an example to see how a unit conversion is setup.

 

A clinical laboratory found that a blood sample contained 0.0026 g of phosphorus and 0.000101 g of iron. Give these quantities in mg, as they are normally reported.

 

Begin with the number you are given. In this case, you have 0.0026 g of phosphorus (symbol P on the Periodic Table) and 0.000101 g of iron (symbol Fe on the Periodic Table).

 

Then set up a ratio using the metric prefix conversions between grams and milligrams, such that the grams cancel each other out mathematically:

 

 Recall from algebra, any number divided by itself is 1. The same applies to units. When a unit is divided by itself, you get 1.

 

Now it's a matter of some elementary math. Multiple the numbers on top, then divide by the numbers on bottom.

example 1.jpg

 

The same can be done for the iron:

 

 

Recall from algebra, any number divided by itself is 1. The same applies to units. When a unit is divided by itself, you get 1.

 

Now it's a matter of some elementary math. Multiple the numbers on top, then divide by the numbers on bottom.

 example 2.jpg

 Often, unit conversion problems involve going through multiple steps. These kinds of problems are worked the same way.

 


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