Glossary
estimate
To estimate, round each number to a named place value (nearest whole number, ten, dollar) and compute with the round numbers, then check the real answer's size against it.
An estimate is a quick, deliberately round answer found by rounding each number to a named place value before computing — the nearest whole number, ten, hundred, or dollar. To estimate 23.7 × 4.1, round 23.7 to 24 and 4.1 to 4, then 24 × 4 = 96; the exact 97.17 is close, which is the point. Rounding follows one rule: look at the digit just after the place you keep, and round up when it is 5 or more. The common errors are rounding only one of the numbers, reporting the exact answer when an estimate was asked for, or rounding to the wrong place. An estimate is not a substitute when an exact answer is required, but when a question asks for an estimate, the rounded result is the answer; otherwise use it to check the size of the exact answer.
Taught in
Related terms
- percent change — A percent change is the amount of change divided by the value you started from, written as a percent: (new − old) ÷ old × 100.
- mean — The mean, or average, is the total of a set of values divided by how many values there are.
Source: OpenStax Prealgebra, Elementary Algebra and College Algebra, first editions (CC BY 4.0); NIST SP 811 (units). Each definition restates the two Mathematics guides in this exam, which carry the per-source citations on their own pages. (OpenStax 1e and NIST SP 811 accessed 2026-10-07)