Snapshot
The calculator is useful, but overuse burns time. Rough work should capture structure, not every keystroke.
Calculator discipline
Use the calculator for arithmetic that is genuinely error-prone: division with awkward numbers, weighted averages, multi-step percentages, and compound growth. Do not use it for every small increase, rounded ratio, or obvious elimination. The calculator should execute your plan, not discover it.
A good scratch line looks like this:
`(new - old) / old`
or:
`weighted total / total weight`
or:
`part / total x 100`
Bad rough work is a pile of numbers without labels. In review, you cannot tell whether a number was a numerator, denominator, intermediate value, or answer.
Screen habits
Numerical items often combine a stem, table, and options on one screen. Build a fixed eye movement:
- •stem first
- •table title and unit line
- •relevant row or column
- •answer options
- •stem again before final click
That final stem check catches many mistakes: "decrease" instead of "increase", "women" instead of "men", "average annual" instead of "total", "percentage points" instead of "percent".
Estimation before exact work
Before calculating, predict the answer region. If 120 rises to 150, the increase is about one quarter, so an answer near 25% is plausible. If options are 12%, 25%, 80%, and 125%, exact calculation is unnecessary. If options are 23.8%, 24.6%, 25.1%, and 25.8%, calculate.
Practice drill
For each wrong answer, write the first wrong action. Examples:
- •used calculator before choosing denominator
- •copied wrong year
- •ignored unit line
- •rounded too early
- •missed "percentage points"
Your rough work should make the mistake visible.