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Calculator guides & worked examples

Calculator guides with practical examples, the formula behind each answer, and the details worth checking.

How to calculate percentage change
Use the original value as the base for percentage change. Work through increases, decreases, reverse changes and percentage points.
How to add and subtract fractions
Find a common denominator, combine the numerators and simplify. Follow worked fraction and mixed-number examples without rounding.
How to simplify ratios and find a missing term
Simplify ratios with a common divisor, align units before comparing, and use a proportion to scale a quantity or find a missing value.
How to calculate weighted grades
Convert scores to percentages, multiply by their course weights and add the contributions. Check weights and unfinished work before calculating.
How to calculate age between two dates
Count completed calendar years, months and days, rather than dividing by 365. Understand Calcr’s leap-day and month-end convention.
How to count days between dates
Distinguish elapsed days from inclusive date counts. Work through leap days, reversed ranges and date addition without time-zone assumptions.