Equal Sum Square Puzzles: How to Fill Every Row and Column
Fill a square so every row and column adds to the same total. The one-gap rule, the centre rule, a worked four by four puzzle and a practice grid.
Riddle10 blog
Articles about math puzzles
Coin Total Puzzles: Largest Unpayable Total and Fewest Tokens
Which totals can two token values pay, what is the largest one they cannot, and how few tokens will do? A ladder method, worked example and practice.
Derangement Puzzles: How to Count Mix-Ups With Nothing in Place
How to count and solve derangement puzzles where no jar, key or tile may stay in its own place, with the counting rule, a table and a clue puzzle.
Counting and Combination Puzzles: How to Count Every Way
Learn when to multiply and when to add, how to count orderings, groups and number splits, and how to avoid double counting, with a worked puzzle.