1 Foundations of Pharmacy Math Free Online FlashCards

What restriction applies to a fraction’s denominator?

A fraction’s denominator is its bottom number; it cannot be zero.

How do you add or subtract fractions?

Rewrite the fractions with a common denominator, then add or subtract their numerators.

How do you multiply two fractions?

Multiply the numerators together and the denominators together; simplify the result if possible.

How do you align decimals for addition or subtraction?

Line up the decimal points so place values are aligned before adding or subtracting.

How do you place the decimal when multiplying decimals?

Multiply as whole numbers, then place the decimal so the product has the total number of decimal places in the factors.

How do you divide by a decimal divisor?

Move the decimal point in both numbers the same number of places until the divisor is a whole number.

Which decimal notation conventions reduce dose-reading errors?

Use a leading zero for values below one, such as $0.5$, not $.5$. Omit trailing zeros in dose expressions: write $5\text{ mg}$, not $5.0\text{ mg}$.

How do you convert between percentages and decimals?

Convert a percentage to a decimal by dividing by $100$; convert a decimal to a percentage by multiplying by $100$.

How do you find a percentage of a quantity?

Convert the percentage to a decimal and multiply by the quantity. For example, $15\%$ of $80$ is $0.15 \times 80 = 12$.

What equation does cross-multiplication produce for equal ratios?

For equal ratios $\frac{a}{b}=\frac{c}{d}$, cross-multiplication gives $ad=bc$, provided the denominators are nonzero.

How should you arrange a conversion factor in dimensional analysis?

Multiply by an equivalent conversion factor arranged so the unwanted unit cancels and the desired unit remains.

How do you round to a specified decimal place?

For ordinary rounding, inspect the digit immediately to the right: leave the retained digit unchanged for $0$–$4$, and increase it by one for $5$–$9$. Round only as directed.