A ratio indicates a connection between two numbers that is separated by a colon.
A colon signifies the use of division. A colon is interchangeable with a division sign.
A proportion is an equation that has two equal ratios. For example: 1/3 = 3/9.
When there is a double colon between two ratios, it indicates an equivalent value between the ratios. A double colon is interchangeable with an equal sign.
The extremes in a proportion are the first and last numbers. For example: in 1/3 = 3/9, 1 and 9 are the extremes.
The means are the second and third numbers in a proportion. For example: in 1/3 = 3/9, 3 and 3 are the means.
When setting up the proportion, you will need to put the ratio in the same arrangement. For example: mg/mL = mg/mL. When you are setting up the proportion remember that one of the ratios will contain an “x” because the amount is unknown. Example: 100mg/5mL = 160mg/xmL)
The second part of the equation is to cross-multiply the means and extremes. Using the above proportion it would look like 100x = 5 x 160.
The final step to determine the dose is to divide both sides by the number before x. Example: 100x/100 = 800/100. This would give you x = 8mL.
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