Between Sums
the sum between the shaded squares

Play Between Sums — Number Sum Puzzle

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Tap then pick a number or ■✎ notes

How to play Between Sums

Every row and every column has exactly two shaded squares; the other squares hold the numbers 1 to N−2, once each (on a 6×6 grid, 1 to 4).

A number outside the grid — on the left of a row or above a column — is the sum of the numbers that sit between that line’s two shaded squares. A sum of 0 means the shaded squares are side by side.

It is a great workout for adding up and for combinations: which numbers can make 7 out of 1, 2, 3 and 4?

How to play Between Sums

Shade two squares in every row and column and write 1 to N−2 in the rest, so each outside number is the sum of the numbers between that line’s two shaded squares.

The rules

  1. Each row and column has exactly two shaded squares.
  2. The other squares of each row and column hold the numbers 1 to N−2, each exactly once.
  3. A number outside the grid is the sum of the numbers between the two shaded squares of that line.
  4. A sum of 0 means the two shaded squares are next to each other.

Playing here

  1. Choose a size and a difficulty, then press New Puzzle.
  2. Tap a square, then a number or ■ on the pad (or type; 0 or space shades). ✎ switches to pencil notes.
  3. A sum turns green when its line is full and adds up, red when it doesn’t.
  4. Hint explains the next deduction — counting, sums and what fits between the shaded squares.

Tips

The full guide, with a worked example and common mistakes: How to play Between Sums.

Questions

What does a sum of 0 mean?

The two shaded squares in that line are side by side, with nothing between them.

Do the shaded squares count?

No — only the numbers strictly between them are added up.

Is there always one answer?

Yes — every puzzle here is checked to have exactly one solution.

How do I solve one from a book?

Open the Between Sums Solver, type the sums and press Solve.

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