Find what repeats across the complete rows, state the rule in words, and substitute every number back into it. A rule that fits only one row is not enough.
How to use these practice puzzles
Use a note or work mentally. There is no time limit on this page, and each answer stays hidden until you open it. The examples below were written for this guide; they are not a list of solutions to numbered levels in the app.
If you enjoy this kind of reasoning, Moocsoft’s Math Riddles / Math Puzzles app offers a separate puzzle journey with hints and solutions. First try the free examples here to see whether the style suits you.
For a row puzzle, keep the direction consistent: use the first two entries to explain the third. For a conventional equation, use normal arithmetic rather than inventing a new meaning for the equals sign.
Puzzle 1: complete a balanced equation
□ + 18 = 47
What number belongs in the box? Think about the operation that reverses adding 18.
Reveal answer and check
29. Subtract 18 from both sides: 47 − 18 = 29. Substitute the result: 29 + 18 = 47. The check matters because it tests the original equation, not just your subtraction.
A missing value may appear on either side of an equation. Rewrite the statement carefully before calculating; 18 − □ = 47 would be a different problem.
Puzzle 2: find the repeated row total
| First number | Second number | Result |
|---|---|---|
| 6 | 9 | 15 |
| 8 | 5 | 13 |
| 7 | 12 | ? |
Use addition to explain the complete rows, then finish the last row.
Reveal answer and check
19. The first two numbers add to the result: 6 + 9 = 15 and 8 + 5 = 13. Therefore 7 + 12 = 19. The rule is the same in all three rows.
Puzzle 3: multiply, then make one adjustment
| First number | Second number | Result |
|---|---|---|
| 3 | 4 | 10 |
| 5 | 3 | 13 |
| 6 | 4 | ? |
Start by multiplying the first two numbers. How far is each product from the displayed result?
Reveal answer and check
22. Each result is the product minus 2: (3 × 4) − 2 = 10 and (5 × 3) − 2 = 13. Apply it again: (6 × 4) − 2 = 22. Do not subtract 2 from one input before multiplying; that changes the grouping.
Puzzle 4: recover the missing input
| First number | Second number | Result |
|---|---|---|
| 2 | 5 | 12 |
| 3 | 4 | 15 |
| 4 | ? | 28 |
This time the blank is an input, not the output. Work backward from 28 using the stated rule.
Reveal answer and check
6. The final row means 4 × □ + 4 = 28. Subtract 4 to get 4 × □ = 24, then divide by 4. Check the complete statement: 4 × 6 + 4 = 28.
Puzzle 5: compare two squared values
| First number | Second number | Result |
|---|---|---|
| 5 | 3 | 16 |
| 7 | 4 | 33 |
| 9 | 5 | ? |
Keep the two squares separate. Squaring a difference is not the same operation as subtracting two squares.
Reveal answer and check
56. The rows give 5² − 3² = 25 − 9 = 16 and 7² − 4² = 49 − 16 = 33. The missing result is 9² − 5² = 81 − 25 = 56. In contrast, (9 − 5)² would be 16.
Choose the next kind of puzzle
If the arithmetic was easy but choosing a rule was difficult, try the hidden-rule strategy guide. If the layout is a list rather than a grid, use the number-pattern walkthrough. If brackets caused mistakes, work through the order-of-operations puzzles.
For new questions on your phone, download the app using the store buttons above. Make an attempt before using a hint, then compare the explanation with your own reasoning. These row examples specify their rule family because a small set of numbers can otherwise support more than one constructed rule.
Common questions
Are these answers for specific Math Riddles app levels?
No. These are original practice examples for the website, not a walkthrough of numbered app levels.
Can a missing-number grid have more than one answer?
Without constraints, a small grid may fit multiple rules. These exercises give a rule or rule family to make the intended task clear.
How should I check a missing input?
Put your answer back into the original equation or row rule and calculate the result again.
Published by Moocsoft, the independent studio behind Math Riddles. Examples and worksheets are illustrative. App features can vary by platform and version; see the store listing for current availability and in-app purchases.