With my K5 math enrichment group, we started a STEM project that combined a variety of skills.  The students were given a list of 8 different challenges (build a bridge, build a tower, build a rocket, etc.) to choose from.  They had to design a plan and figure out what materials they would need to "buy" from me.  Popsicle sticks, cups, aluminum foil, etc. all cost a different amount.  Students needed to add up their total and make sure they didn't "spend" more than $10.00 on materials.  As the students were filling out their planing sheets, I realized they did not know how to fill out the materials spreadsheet... great opportunity for a mini lesson!  Some of the challenges had a specific height requirement (tower had to be at least 20 cm tall).  This lead to another great mini lesson on what is a centimeter, how is it different than an inch, and how to use both the metric and customary sides of a ruler.  Finally, as the students were buying and returning materials they needed to exchange, it provided more great opportunities for mini lessons on how to add and subtract money.  Again, this project took longer than I anticipated but it was worth it!  My students learned money, measuring, adding, subtracting, and engineering skills during this very engaging STEM activity.  I also found it interesting that I had 10 groups and only 3 of them chose the same challenge.  It was so fun to see a variety of projects in the end.