App review by Amanda Bindel, Common Sense Education | Updated July 2012
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Sudoku-like puzzler uses all four math operations

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Subjects & Skills
Math, Critical Thinking

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Pros: Kids compete with themselves to improve time, skills.

Cons: No hints or strategies are available to help scaffold learning.

Bottom Line: Challenging game makes math practice fun.

NineGaps is a fun way for students to get daily math practice, and it's a great brain workout. Use it as a daily warm-up activity, letting kids play for five minutes before instruction begins. It's also a fun homework activity for daily math skills practice in all operations. Teachers could inspire fun internal competition for kids to beat their own best times by offering some type of recognition for personal records.

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NineGaps is a Sudoku-style game that allows kids to practice arithmetic in a race against time. Kids drag digits 1 through 9 to empty slots in a 3x3 grid of equations, using each number only once. The numbers must be placed so vertical and horizontal equations are all correct. Five challenge levels allow kids at multiple ability levels to play. Addition, subtraction, and multiplication are included in each level; division appears in some levels. When numbers for an equation are placed so the equation is true, chimes play. Trumpets play when an equation is incorrect. To swap numbers, drag one number on top of another and they trade places. The game's high score list shows the fastest time for each level.

NineGaps is a fast-paced, entertaining math game. Rules are simple, and multiple levels provide different levels of challenge. Kids can try to beat their previous times on each level, and as they play, they'll improve their arithmetic skills. The self-evaluation involved with trying multiple solutions transfers well to other problem-solving areas. Other than choosing a playing level, no customization -- such as choosing operations for each puzzle -- is possible. Though more helpful feedback and math tips would give kids room to learn -- not just practice -- math, NineGaps is a challenging way for kids to strengthen existing math skills.

Overall Rating


Very challenging and fun math puzzler sure to be a hit with kids who love puzzles and math. Math-averse kids also may be engaged if they have a competitive streak.


No instruction is included for math problem solving, but kids will strengthen math skills and algebraic thinking by solving multi-operation puzzles. Math is baked into every aspect of play, which will tranfer well to other activities.


Kids can see their best times and compare it to others if they opt in to the Game Center. Game play instructions are clear and easy to understand, but no math help is available.

Common Sense reviewer
Amanda Bindel Classroom teacher

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Featured review by
Susan M. , Other
Soduko-style basic math fact practice platform with a focus on problem-solving
This is a great support tool to have as part of a larger repertoire of learning math fact strategies. Students who are visual-spatial and struggle with linear timed tests or drill practice may like this slant because they are trying to find just the right combinations to complete the puzzle. I like how students can use trial and error with the puzzle and found that because of that, students remember their facts better and could visualize rather than just memorize. There are also levels, which worked wel ...
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