About Cross Addition Puzzle
This is arithmetic wearing the clothes of a logic puzzle. A grid has some numbers filled in and target sums along its edges, and the child has to work out what belongs in the empty boxes. Because every number affects both a row and a column, guessing rarely works - the child has to reason about constraints, which is a genuinely different mental activity from answering sums one at a time.
What this game teaches
- Addition of several numbers held in mind at once
- Working backwards from a total to a missing part
- Using one solved cell to constrain the next
- Checking an answer against two conditions rather than one
- Persistence with a problem that cannot be solved in a single step
How to play
- A grid appears with target sums shown for each row and column.
- Tap an empty box and enter a number.
- Fill every box so all row and column totals match their targets.
- Use Check Answer to test the grid; thirty levels increase the grid size and number range.
Before you start
A child needs confident addition within twenty and the patience to try something, find it wrong, and try again. This is not a first arithmetic activity - it assumes the sums themselves are easy and the difficulty is the reasoning.
For teachers
Excellent for pair work, because the reasoning becomes visible when children have to explain a placement to each other. Ask them to start with the row or column that has the fewest blanks; children who start in the middle of the grid usually stall. Suits Class 3 upward, and the later levels are a genuine challenge for Class 6.
For parents
Resist the urge to point at the right box. Instead ask 'which line has the least missing?' and let them find the entry point themselves - that question is the whole skill. If a child is stuck for more than a few minutes, solve one cell together and hand it back.
Related games
- Bead Counting — Class 1-2
- Time Recognition Game — Class 2-5
- 1 to 100 Digits — Class 1-4