This is a fun way to practice arithmetic while decoding a secret message. Each math problem you solve gives you a key to decode one letter of the message.
Create your own messages to be solved online, or print them out as a worksheet to be done with pencil and paper.
Try it here:
https://depsypher.github.io/mystery-message/
To create a message, start typing in the message box. The Problem box shows what the Mystery Message will look like. The Parameters box lets you customize the problems.
By default the site will create random addition problems with answers ranging from 0-9. If your message has more letters than that, the answer range will automatically increase. You can change the answer range to be higher for more difficult problems, and choose a mix of addition, subtraction, multiplication and division. If you don't like a particular problem (you might feel there are too many in the form "zero plus number equals number" for example) you can click on it to generate a new one. It's possible that it'll randomly generate the same one again though, or that there's only one way to formulate a particular answer given the parameters, so clicking again won't always get you a new problem.
When you're happy with the message and the problems, click "Solve" to get the Mystery Message. This page can be filled out online directly or printed out nicely formatted using the print button on the top right of the page. The Mystery Message page can be shared, as all the info is contained in the (usually rather long) url. The solution is obfuscated in that url so you can't "cheat" by looking at the url to see the answer without solving the problems.
Other things to note: Emoji's are fair game in the mystery message, so have at it! The site should work well on iPad or other tablets, but at the moment it's not really designed to fit well on a phone sized screen.
I have a 1st grader who enjoys learning to read, but math is a struggle.
Attempts to get her to practice were pushing her into a attitude that she "hates math". Workbooks were too tedious and the iPad Apps I found did little to make it fun.
I'm not sure where the idea came from, but one day I hand-made a "mystery message" on paper for her with addition problems and she loved it. She asked for another one. After that I made this online generator and the first time we used it she asked to make five of them in a row, diligently working though each of them one by one.
I hope it sparks the same enthusiasm in other kids out there.