When I teach Mystery Math I tell the students that I am the only teacher they will ever have that will simply give them the answer. I always begin by writing the answer on the board. It should look something like, "The answer is 7 flowers."
The goal is to have the students work backwards by starting with the answer and using that to determine what operation and number sentence they could use to solve a problem that has in this case, 7 flowers as the answer. This is challenging work for 2nd grade students, but with support I know that this practice in thinking quantitatively, decontextualizing and contextualizing problems, makes a difference in their ability to navigate word problems (MP2).
Write the number sentence ___ + ___ = 7 on the board. Have the students turn and talk about if they were to choose the operation of addition what could they use as addends to get the sum of 7?
Students should be able to come up with a number of choices such as 1 + 6 = 7, 2 + 5 = 7, 3 + 4 = 7, etc. This helps the students to realize that there are multiple number sentences for one answer. It also encourages them to try different operations and strategies. I've included two examples here (Mystery Math Example 1, Mystery Math Example 2) here to show the expectations, and the work 2nd grade students can do, when given clear expectations, modeling, and frequent practice.
Once the community decides on a number sentence to begin with (my students chose 7 + 0 = 7), you need to next determine what words you are going to use. I often prompt the children to turn and talk to their group or a neighbor about what they could write as a word problem for 7 + 0 = 7 flowers.
Once they have had an opportunity to talk, decide as a class which problem you will write together for the first day. Write the problem your students chose (We did: Ms. O'Connor had 7 flowers. She got 0 more. How many flowers did she have in all?)
I always make sure to put an emphasis on the question. Students copy the word problem in their Mystery Math notebook. It is important to guide students in using their notebook. As aforementioned, this is more a lesson about routine. The students will use this notebook setup for every Mystery Math daily problem.
Finally, I prompt the students to think about creating a word problem as a recipe. The best chefs add things to their dishes to make them taste better or to become more exciting. We, as mathematicians, need to do the same thing when creating word problems. The extra "spice" in this recipe is the picture. I always encourage my students to draw a picture to show their understanding of the problem. A picture is not required to solve the problem, but it makes quite a difference when assessing a students true understanding of the concept, operation, and/or strategy.
Make a list of all of the recipe ingredients together on the board. Eventually you will use this recipe card as a tool to help guide students through the process of writing a word problem. My students keep it in their math folder so that they may reference it if they get stuck on a step.
I use Mystery Math as a daily activity for students. It is recommended that you continue with a gradual release of responsibility. The first few days of Mystery Math, the problems should be completed together with students creating the word problems as a class, then they will begin to work in partners to create word problems, ending with their creation of word problems on their own.
Student work should be checked regularly to ensure understanding. As new concepts are taught it is recommended that students be asked to utilize those new concepts in Mystery Math. For example, after students are taught to add three numbers (9 + 3 + 4) they should then be asked to create a word problem to show their understanding.
Because this is an on-going, daily activity there is not a true summarizer for this lesson. However, at the end of each week I ask permission of the students to share a few word problems that they have created. I typically write the word problem the students have written on the board, and challenge the students to either work independently or in partners (depending on the level of difficulty of the problem) to write a number sentence, draw a model, and solve the word problem. The students are extremely motivated by this, as they all want to be chosen as one of the problems shared on Friday!