The number notes
Make sense of the numbers.
Clear examples for everyday decisions. Browse a topic, see a worked example, and try the calculation with your own numbers.
A small collection
Percentages and prices
Find the base, the change, and the price you will actually pay.
01How to find a percentage of any numberTurn “18% of 240” into one multiplication, then check the scale.2 min 02Percentage change: choose the starting valueMeasure a rise or fall without mixing up the old and new amounts.2 min 03Find the price after a discountCalculate the amount saved and the final price from an advertised percentage.2 min 04Work backwards from a percentage amountRecover the original whole when you know only a part or reduced price.2 min 05Find the tax already included in a totalSeparate an inclusive total into pre-tax amount and tax without double counting.2 min
A small collection
Bills and plans
Share costs, build a simple plan, and understand a fixed payment.
01Split a bill with a tip, step by stepChoose the tip base, add it once, then divide the whole total.2 min 02Share a bill fairly when orders differAllocate a shared charge in proportion to each person’s own order.2 min 03Calculate what is left in a monthly budgetPut income, essentials, flexible spending, and planned saving on the same period.2 min 04How long will a savings goal take?Estimate a target date from a fixed contribution without assuming interest.2 min 05What a fixed loan payment coversSeparate principal, interest, term, and the total cost of a standard amortizing loan.2 min
A small collection
Units and currency
Convert with the right unit, definition, and rate date.
01Convert kilometres and miles without losing the unitUse a defined length factor and check which direction you are converting.2 min 02Celsius and Fahrenheit: convert the whole scaleTemperature conversion needs an offset as well as multiplication.2 min 03US and UK gallons are different sizesAvoid a quiet volume error by naming the gallon before converting.2 min 04GB and GiB: why a file size changesDistinguish decimal and binary prefixes when comparing storage sizes.2 min 05How to read a currency conversion rateShow the quoted base currency, date, and distinction from a transaction price.2 min
A small collection
Dates and time
Count days and turn recurring amounts into useful totals.
01Count the days between two datesName the start, end, and whether the start day counts.2 min 02Inclusive date counting for a planned periodKnow when both the first and last day belong in a total.2 min 03Add a number of calendar days to a dateFollow the day count across month and year boundaries.2 min 04What a leap year changes in date mathsHandle 29 February correctly when counting or moving across February.2 min 05Turn a daily cost into a monthly estimateState whether “per day” means every day, weekdays, or selected days.2 min
