Split-the-Bill Demon

A mental math game about splitting the bill for a table of shared dishes. Coupons and organizer discounts make it harder and harder.

How to play

1. Choose a level and press Start. There are 10 questions.
2. A receipt appears. It lists the price of each dish and who ate it.
3. Work out how much the person in the question pays, and type the number. Confirm with the Answer button or the Enter key.
4. After you answer, the calculation is shown step by step. Press Next question to go on.

The calculation rules

• Shared dishes: A dish is split equally among the people listed for it. If it says "Everyone", it is split among all of them. Questions that do not divide evenly never appear.
• One person's total: Add up the shares of every dish that person ate.
• Extra rules: The rules marked with "※" under the receipt are applied from top to bottom. The order is always: coupon (10% off) → tax (add 10%) → organizer discount (¥500 off) → rounding up (to the next 100 yen).
• Organizer discount: Only the organizer gets it. If the person being asked about is not the organizer, this rule does not affect them.

The four levels

• Easy: 3 people, 4 dishes, no extra rules. Prices are in multiples of 100 yen.
• Normal: 4 people, 5 dishes, one extra rule (tax or the organizer discount).
• Hard: 4 people, 6 dishes, two extra rules. Prices are in multiples of 50 yen.
• Demon: 5 people, 7 dishes, three extra rules (rounding up is always one of them). Prices are in multiples of 10 yen, so the middle of the calculation is full of odd amounts.

Score and titles

A correct answer is worth 100 points, plus up to 50 bonus points depending on the time left. The time limit for each question is 45 seconds on Easy, 60 on Normal, 75 on Hard and 90 on Demon. The maximum score for 10 questions is 1500. Your number of correct answers decides your title, from "Careful, overpaying" up to "Split-the-Bill Demon" (all 10 correct). Your best score is saved in your browser only, and is not sent to any server. You can copy your result as text with the "Copy result" button.

Tips

• Find the name in the question. On the receipt, that person's name is highlighted. Pick out only those dishes.
• 10% is a one-digit shift. 10% off ¥1,300 is ¥130 off, so ¥1,170. Adding 10% tax means adding ¥130.
• Follow the fixed order. The extra rules always come in the same order. Go from the top and you won't get confused.
• Round up last. Ignore odd amounts along the way, and only round to the next 100 yen at the end.
• If unsure, enter a guess. Answering with a close number and reading the explanation teaches you more than running out of time for zero points.

FAQ

Are the prices and names the same every time?

No. Every question is generated randomly, so you almost never see the same one twice.

Can I use a calculator?

The rules allow it, but the fun of this game is doing it in your head. Try it without a calculator within the time limit first.

Will I ever get an amount that doesn't divide evenly?

No. Every answer is a whole number of yen.

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