Math: Problem-Solving and Data Analysis

A ratio compares two quantities of the same kind (e.g., 3 boys : 2 girls). A rate compares two quantities with different units (e.g., 60 miles per hour).

Cross-multiply: a·d = b·c, then solve for the unknown variable.

It scales the proportional quantity by the same factor. If y = kx and x is multiplied by 4, then y is also multiplied by 4.

Set up a proportion from the scale ratio: (drawing length)/(real length) = scale ratio, then solve.

A unit formed by combining base units, e.g., kWh (energy), people per km^2 (population density), or m/s (speed).

Multiply by a conversion factor (a fraction equal to 1) arranged so the unwanted unit cancels.