Measures and accuracy Study Guide

Estimate by replacing numbers with convenient rounded values, then calculate an approximate answer. Use this estimate to judge whether an exact or technology-generated result is sensible. If the result is very different from the estimate, recheck the input, operation, decimal point and calculator entry.

When a measured value is rounded, its lower bound is half a rounding unit below the stated value and its upper bound is half a rounding unit above it. For a combined quantity, choose the endpoint values that make the result smallest and largest. Products of positive quantities use lower × lower and upper × upper. For a quotient of positive quantities, the minimum is lower numerator ÷ upper denominator, while the maximum is upper numerator ÷ lower denominator. For subtraction, the minimum uses the lower first quantity and upper quantity being subtracted; the maximum uses the upper first quantity and lower quantity being subtracted.