Glossary
decimal
A decimal writes a fraction using place value after a decimal point, so 0.75 means 75 hundredths, and the alignment of that point governs every operation.
A decimal is a way of writing a fraction with place value: everything after the point counts tenths, hundredths, thousandths and so on, so 0.75 is 75 hundredths and 0.075 is 75 thousandths. That is why the trailing zero changes the number and a leading zero after the point does not: 0.5 and 0.50 are the same value, 0.05 is ten times smaller. Adding and subtracting require the points lined up vertically, because only digits in the same place value can be combined; multiplying does not, and the answer simply carries as many decimal places as the two factors had between them. To divide by a decimal, move the point in both numbers until the divisor is whole. In measurement and dosage, the count of decimal places is also a safety device — a misread point turns 0.5 mg into 5 mg.
Taught in
Related terms
- rounding — Rounding replaces a number with a near one at a chosen place value, using the digit after it: five or more rounds up, less than five rounds down.
- order of operations — The order of operations is the fixed sequence for evaluating an expression: parentheses, exponents, multiplication and division left to right, then addition and subtraction left to right.
- metric prefix — A metric prefix names a power of ten applied to a base unit — kilo is 1,000, centi is one hundredth, milli is one thousandth — so converting between them moves the decimal point.
- percent change — Percent change measures a change against the starting value: the amount of change divided by the original, then written as a percent.
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)