Glossary — Ratio

Compound measure — a measure made by combining two different units, such as metres per second.

Constant of proportionality — the fixed number that links two quantities in a proportional relationship.

Density — mass per unit of volume.

Direct proportion — a relationship where one quantity is a fixed multiple of another.

Growth factor — the multiplier that gives a new amount after growth, such as $1.08$ for an increase of $8\%$.

Inverse proportion — a relationship where one quantity increases as another decreases, so their product stays constant.

Lower bound — the smallest value a rounded measurement could have had.

Percentage change — the increase or decrease written as a percentage of the original amount.

Pressure — force per unit of area.

Ratio — a way to compare amounts by showing how many parts of each amount there are.

Rate — a comparison of two quantities measured in different units, such as kilometres per hour.

Reverse percentage — a method for finding an original amount from a value after a percentage change.

Scale factor — the multiplier that changes a length from one similar shape or drawing to another.

Scale drawing — a drawing where every length has the same ratio to the matching real length.

Simple interest — interest calculated each time on the original amount only.

Standard form — a way to write a number as $a\times10^n$, where $1\leq a<10$ and $n$ is an integer.

Uncertainty interval — the range of values that could round to a stated measurement.

Unitary method — a method that finds the value of one unit before finding the value of several units.

Upper bound — the largest value a rounded measurement could have had.

Volume scale factor — the multiplier between the volumes of similar solids; it is the cube of the length scale factor.