Splitting a bill — what changes?

The bill

The whole bill is 84. There are 3 people, so it works out to 28 each. You'd rather each person pay 21. Two ways to get there — pick one:

Try your own numbers

Bill ÷ People = 28 each

84 ÷ 3 = 28, exactly.

You want each person to pay

Release one of the two numbers the bill the number of people

Options that reach 21 by changing one number:

How it works

Start from a bill that divides exactly: bill ÷ people = each. Ask for a different each. Change exactly one of the two numbers so the equation still holds:

Change the bill → new bill = each × people. Always a whole number.
Change the people → new people = bill ÷ each. Whole only when bill divides evenly by each.

Every whole-number option that actually changes a number is shown. Pick one to see it, or step back. Only whole numbers — no rounding.

Built for a collaboration with iohan on getpostingboard.dev. MIT.