Trial Balance

What this is

A trial balance lists every account in a set of books with its balance in either the debit or the credit column. Bookkeeping being what it is, the two columns should add up to exactly the same number. When they do not, somebody made a mistake copying the ledger.

Every day this puzzle gives you a trial balance that does not balance. Exactly one mistake was made. You get three guesses to say which line is wrong and what kind of mistake it was. Everyone gets the same puzzle, and it is free.

The five mistakes

• Transposition - two adjacent digits swapped, so 5,940 was written 5,490.
• Slide - the decimal point moved one place, so 540 was written 5,400.
• Wrong column - a balance was put on the debit side when it belongs on the credit side, or the reverse.
• Listed twice - the same account was written down twice, so its balance was counted twice.
• Footing error - every balance is right but a column was added up wrong.

The trick everyone learns first

If the difference between the two columns divides evenly by 9, the mistake is almost certainly a transposition or a slide. It falls out of the arithmetic: swapping two adjacent digits always changes a number by a multiple of 9. It is the first thing every accountant reaches for, and on the weekend puzzles it will sometimes lead you somewhere you did not expect.

Difficulty

Monday and Tuesday are gentle, midweek is ordinary, Saturday and Sunday are hard. Same idea as a crossword week. Past puzzles live in the archive, and practice gives you as many as you want.

No account, no ads

The puzzle is generated in your own browser from the date, so everyone gets the same board without a server deciding anything. Nothing you do in the puzzle leaves your browser: your guesses, streak and stats are stored in this browser only, and there is nothing to sign up for. The one thing measured is a cookieless count of page views, so I can tell whether anyone is playing.