Ledger Check

Eight lines of debits and credits, an opening balance, and a closing balance from the statement that the column refuses to agree with. Exactly one entry was mistyped, and the size of the difference tells you what kind of mistake it was: a difference that divides by 9 is two digits transposed or a decimal point one place out, and a difference that is exactly twice an entry was posted on the wrong side. Every board is checked before it is dealt — the whole catalogue of single-entry corrections is enumerated, and only one of them closes the column — so the answer is provable, never a guess.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Read the three totals under the sheet. The column closes at one figure, the statement says another, and the difference between them is the only clue you need. Its direction matters too: the sheet tells you whether the statement is higher or lower than the column.
3. Test the difference for 9. Add its digits; if they come to a multiple of 9, so does the difference. Divide the difference by 9. If the answer is one of the printed amounts — or a tenth of one — that line's decimal point slid a place. Otherwise the answer reads as a single digit followed by zeros: the digit is the gap between the two transposed digits and the zeros count the decimal place, so look for a line with that gap between two adjacent digits in that position.
4. If it does not divide by 9, halve it. An amount posted as a debit instead of a credit moves the balance by exactly twice itself, so half the difference names the entry outright.
5. Move down the sheet with the up and down arrows. Left and right walk the same column.
6. Press F to check a line off once you have ruled it out. That costs nothing and you can do it as often as you like; Esc takes the mark back. On a phone, tap the circle at the end of a line.
7. Press Enter to name the line under the cursor as the mistyped one. That is the only move that costs a try, so it is never a single tap on a phone — select the line, then press the Name line button. Get it right and the sheet tells you exactly what the typo was.

How do you find a mistyped entry in a ledger that will not balance?

Work from the difference, not from the entries. Total the column, subtract it from the balance you were given, and look at what is left over. If that difference divides by 9, the figure itself is right but its digits are in the wrong order or the decimal point is in the wrong place: dividing by 9 gives you a number of the form "one digit followed by zeros", and that digit is how far apart the two swapped digits are while the zeros tell you which decimal column they sit in. If the difference does not divide by 9, halve it and look for an entry of exactly that amount — an amount entered on the wrong side moves a balance by twice itself, because you have to take it off the wrong column and put it on the right one. Between them those two tests find the great majority of single-entry typing mistakes without re-checking a single figure against its source document.

Why does a transposition always divide by 9?

Because swapping two adjacent digits only ever moves value between two neighbouring decimal columns. Write the two digits as d and e sitting in columns worth ten times and one times some place value. Before the swap they contribute 10d + e; after it, 10e + d. The change is 9(e − d) — nine times the gap between the digits, times the place value. That is why the ninth of the difference is always a single digit followed by zeros. A decimal point that has slid a place divides by 9 too, for the same reason: turning an amount a into 10a changes the balance by 9a. Telling the two apart is one extra look — if the ninth is a printed amount, it is a slide; if it is a lone digit with zeros after it, it is a transposition.

Is there always exactly one answer?

Yes, and it is proven rather than assumed. A correct ledger is drawn first, so the stated closing balance is true by construction and can never itself be the error. Exactly one entry is then corrupted. Before the board is dealt, every single-entry correction the game allows — each adjacent transposition of every line, each decimal slide, and each wrong-side posting — is enumerated and tested, and the board is kept only if one of them closes the column on the stated balance. If two lines could explain the difference, the sheet is thrown away and redrawn.

What happens if I name the wrong line?

You spend one try and the line is struck out, so the elimination is recorded for you. When the tries run out the round ends and the sheet shows which entry it was and what the mistake was. You get one try for each line that survives the divide-by-9 test, plus one, so an easy board gives two and a board where three lines look plausible gives four. Checking a line off by hand is always free and unlimited — the tries exist to stop guessing standing in for the diagnosis, not to punish thinking.

Is there any money, betting or in-app purchase in this?

None, and there never will be. The rupee amounts on the sheet are made up by the generator and are worth nothing. There is no currency, nothing to buy, no hints to unlock for a fee and no prizes.

Does it work offline?

Yes. Once the page has loaded once, the whole game — the ledger generator, the catalogue of typing mistakes and the solver that proves only one answer exists — sits on your device. No server is involved in play at any point, and no figure you look at ever leaves the browser.

Can I play it with a keyboard or a screen reader?

Both. Arrows walk the sheet, F checks a line off, Esc takes the mark back and Enter names a line. Every line is announced with its reference, its side in words, its amount, the balance after it and whether you have checked it; the live region reads out both totals and the difference between them. The side of an entry is spelt out as Dr − or Cr + in text, a checked line carries a ✓ and a ruled-out line carries a ✕ with its reference struck through, so nothing on the sheet depends on telling two colours apart.

Eight lines, one opening balance, one mistyped entry. Amounts run from ₹10.00 to ₹9,999.99 and are held as whole paise throughout — ₹1,240.50 is stored as 124050 and stays 124050, so no rounding ever creeps into a total. Three kinds of mistake are dealt and searched for: two adjacent digits transposed, the decimal point moved one place, and an amount posted on the wrong side. Non-adjacent transpositions, two mistakes on one sheet and an error in the stated balance itself are all out of scope, which is exactly what makes the answer provable. The running balance never goes overdrawn, so a negative figure in the balance column is never a clue.

Cut Share and Weight Split are the other two number games that turn on exact totals rather than arithmetic speed. Amount to Words and the GST calculator are the tools that work in the same integer paise this game does.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.