Glossary
unit rate
A unit rate is a rate reduced to one unit — dollars per item, kilometers per hour, milligrams per milliliter — which is what makes two offers comparable.
A unit rate is a rate reduced to one unit: dollars per one item, kilometers per one hour, milligrams per one milliliter. Reducing to one is what makes two offers comparable, because the numbers then share a scale. A pack of 12 for $4.80 works out at $0.40 an item; a pack of 20 for $7.00 works out at $0.35 an item, so the second is cheaper even though its price is higher. The method is two steps: divide the amount by the count to get the rate for one, then multiply by the count you actually need. The step people skip is the second one, because a unit rate is not the answer to a question that asks for a total. Rates also travel in both directions: a rate given as kilometers per hour becomes minutes per kilometer when it is inverted, which is what a question about pace asks for. Write the units on both sides of the division and the direction stays visible.
Taught in
Related terms
- proportion — A proportion is a statement that two ratios are equal, with one of the four values missing — and the missing value is what the calculation returns.
- ratio — A ratio compares two quantities, written a : b, and it stays the same when both sides are multiplied or divided by the same number.
- denominator — The denominator is the bottom number of a fraction: how many equal parts the whole is divided into, and therefore the size of each part.
- IV rate — An IV rate is the volume an infusion delivers per hour, found by dividing the total volume by the number of hours it runs.
Source: The math guides in this course (ratio and proportion, measurement and conversion, dosage calculation): every definition and worked value above was written for this course, because arithmetic and unit conversion are not a publisher's prose, and each guide shows the method worked. Elsevier's own HESI A2 page, which names math among the areas the exam covers, is the exam-side source. (Elsevier HESI A2 page accessed 2026-10-23; definitions written 2026-10-27)