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Sum to Twenty Puzzle by Marcy Cook

Today I’m sharing with you the Sum to Twenty Puzzle by Marcy Cook.

sum to 20 puzzle

In Math Concepts, we ran out of That’s Logical puzzles a few weeks ago, so I had to find a new source of daily warm-ups. Instead, I’ve started using puzzles from “THINK ABOUT IT! Mathematics Problems of the Day” by Marcy Cook.

This book was published by Creative Publications in 1982, and for once I would not recommend ordering a copy off of Amazon.

Think About It by Marcy Cook

If you already happen to have a copy, cherish it and don’t let anyone borrow it!

Wednesday, I put this sum to twenty puzzle up on the board. And, I challenged my students to solve it on their individual white boards.

Sum to Twenty Puzzle by Marcy Cook

This. Did. Not. Go. Well.

Students were confused by the fact that there were already two fours in the puzzle. Students were confused whether they had to use each number between 0 and 9 only once or if they could use some more than once and others not at all.

I ended up encouraging my students to write the numbers 0-9 on their dry erase board so that they could mark off each number as they used it.

This still did not go well. Students were bringing me their whiteboards to check their answers, and it was clear that they had misunderstood the instructions. Many had made each row sum to twenty without worrying about the columns.

These students do tend to struggle more than most. This is part of the reason they are in Math Concepts, a class created for our 9th graders who are not yet ready for Algebra 1.

After telling student after student that their answer was incorrect, I eventually decided we needed to stop this activity and regroup. I told them to put their dry erase boards away with the promise that we would tackle this puzzle again the next day.

Sum to Twenty Puzzle by Marcy Cook

A few minutes on the computer and some quality time with my laminator led to a version of this puzzle with moveable pieces.


drawing of laminator machine with text "laminating recommendations"

A laminator is a MUST-HAVE for me as a math teacher! I spent my first six years as a teacher at a school with a broken laminator, so I had to find a way to laminate things myself.

I’ve had several laminators over the years. I currently use a Scotch laminator at home and a Swingline laminator at school.

I highly recommend splurging a bit on the actual laminator and buying the cheapest laminating pouches you can find!

The next day, my students seemed reluctant to try the sum to twenty puzzle again until they realized that it was in a slightly different form. With the moveable pieces, they jumped into the puzzle with a bit of excitement.

Sum to Twenty Puzzle by Marcy Cook

Within only a few minutes, my students started announcing that they had solved the sum to twenty puzzle. It was adorable to watch them attempt to cover their solution from the prying eyes of their classmates. I’ve had issues with this class sharing puzzle answers, so it was especially good to see this.

Sum to Twenty Puzzle by Marcy Cook

This was no longer an impossible puzzle but a puzzle with a solution worth working towards.

Sum to Twenty Puzzle by Marcy Cook

There’s another variation of this sum to twenty puzzle that sums to 21 in the book that I look forward to trying with my students after this whole strike business is over.

Sum to Twenty Puzzle by Marcy Cook

This puzzle would be a great addition to a puzzle table, as well!

Digital Version

Google Slides

Cathy has converted the Sum to Twenty Puzzle to a Google Slide Presentation.

Sum to Twenty Puzzle in Google Slides

Danita Forbes has also created a version of this puzzle.

Sum to Twenty Puzzle in Google Slides

Puzzle Solutions

I intentionally do not make answers to the printable math puzzles I share on my blog available online because I strive to provide learning experiences for my students that are non-google-able. I would like other teachers to be able to use these puzzles in their classrooms as well without the solutions being easily found on the Internet.

However, I do recognize that us teachers are busy people and sometimes need to quickly reference an answer key to see if a student has solved a puzzle correctly or to see if they have interpreted the instructions properly.

If you are a teacher who is using these puzzles in your classroom, please send me an email at with information about what you teach and where you teach. I will be happy to forward an answer key to you.

More Magic Square Puzzles


Friday 24th of August 2018

Hi Sarah! Quick question, when you laminate these squares, do you laminate the entire sheet then cut them out, or do you cut them out first and then laminate?

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