Lesson 3 Metric Conversions Using Dimensional Analysis
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Lesson 3 – Metric Conversions Using Dimensional Analysis
Objectives
Identify conversions used in dimensional analysis
Demonstrate use of metric conversions in dimensional analysis
There are times when you need to convert the information in a medication math problem from one measurement to another. Here is a table with the basic conversions you will need to know for medication math.
The conversions
1 tsp = 5 mL 1 tbs = 15 mL 1 oz = 30 mL 1 lb = 16 oz 1 kg = 2.2 lb 1 L = 1000 mL Microdrip = 60 gtts/mL 1 g = 1000 mg 1 mg = 1000 mcg 1 hr = 60 min
Basic Setup
Setting up medical math calculations is challenging but dimensional analysis (DA) simplifies the process. The starting point of setting up the DA grid is dependent on what the question is asking for. The desired outcome gets placed in the top left hand corner of the DA grid. Refer to the examples below.
How many milliliters (mL) are in 8 ounces (ozs)
o The question is asking to solve for mL, which is placed in the top left corner of the grid as the starting point
mL
o Next, a pair is placed in the box; in this instance, we are placing a standard conversion
30 mL 1 oz
o Whatever measurement is on the bottom of the initial box gets placed in the next column in the top box
30 mL oz 1 oz
o Now, place the number from the question next to the measurement
30 mL 8 oz 1 oz
o Cross out the top measurements that match the bottom measurements from right to left across the grid
30 mL 8 oz 1 oz
o When completing the grid, multiple across the top from left to right and do the same for the bottom
o Finally, divide the top number by the bottom number to obtain what we are solving for, which is mL
30 mL 8 oz 240 240 mL SET & SCM 6.14 Lesson 3 – Metric Conversions Using Dimensional Analysis 1 oz 1
Convert 18 grams (g) to milligrams (mg)
o The question is asking to solve for mg, which is placed in the top left corner of the grid as the starting point
mg
o Next, a pair is placed in the box; in this instance, we are placing a standard conversion
1,000 mg 1 g
o Whatever measurement is on the bottom of the initial box gets placed in the next column in the top box
1,000 mg g 1 g
o Now, place the number from the question next to the measurement
1,000 mg 18 g 1 g
o Cross out the top measurements that match the bottom measurements from right to left across the grid
1,000 mg 18 g 1 g
o When completing the grid, multiple across the top from left to right and do the same for the bottom
o Finally, divide the top number by the bottom number to obtain what we are solving for, which is mg
1000 mg 18 lb 18,000 18,000 mg 1 g 1
Well done! Now you have the tools to correctly calculate conversions for safe medication administration.
Here are some additional practice problems:
o How many milligrams (mg) are in 4.6 grams (g)
o How many grams (g) are in 300 milligrams (mg)
o How many milligrams are in 2,500 micrograms (mcg)
o How many micrograms are in 4 milligrams (mg)
o How many teaspoons (tsp) are in 20 milliliters (mL)
o How many tablespoons (tsp) are in 1 ounce (oz)
SET & SCM 6.14 Lesson 3 – Metric Conversions Using Dimensional Analysis o How many teaspoons(tsp) are in 3 tablespoons (Tbs)
o How many milliliters (mL) are in 1.3 liters (L)
SET & SCM 6.14