Choosing the accuracy of a final answer

How many figures an answer should carry, given the accuracy of the inputs.

Rounding during a calculation

Why intermediate values are kept at full accuracy until the final answer.

Estimating by rounding to one significant figure

Rounding every number to one significant figure, then calculating exactly.

Over-estimates and under-estimates

Judging each rounding by the role its number plays in the calculation.

Estimating powers and roots

Trapping a number between the nearest squares or cubes to estimate its root.

Higher

Checking an answer is sensible

Testing a result against an estimate, the context, and the inverse operation.