Cooking Up a Storm in Math

Today in math we learned about using new measuring tools: measuring spoons and measuring cups.  What better way to learn about them than by using them?!  Given the time and kitchen restrictions, we whipped up a batch of rice krispie treats in class (with a side secret field trip to the teachers' room for the microwave!).

Here is the recipe:
3 tablespoons butter
40 large marshmallows
1/3 cup peanut butter
2/3 cup chocolate chips
6 cups rice krispies

(Melt butter, marshmallows, and peanut butter on low heat.  Pour into a large mixing bowl.  Add rice krispies, stirring.  Stir in chocolate chips.  Coat a 13x9 pan with butter/spray.  Using a buttered spatula, spread the mixture in the tray.  Cut when cooled.)


The kids measured and mixed.  We then looked at our recipe and our tray full of gooey goodness and tried to figure out how many cups of ingredients went into the pan.  We guessed that the marshmallows were about 2 cups, so we wrote 2 c (marshmallows) + 6 c (rice krispies) + 1/3 c (pb) + 2/3 c (chocolate chips) = ?  We added the integers easily and then took a look at the fractions.  I drew a pie with one third shaded to represent the pb, then a separate pie with two-thirds shaded to represent the chocolate chips- before I was done shading, the hands shot up!  They recognized that 1/3 + 2/3 = 3/3 or 1 whole.  Wow!  After we left our tray of treats to set, we had to figure out how to divide the pan up equally.  Aiden counted 14 kids plus one teacher, so we needed 15 pieces.  We drew the rectangular pan on the board and looked at ways we could divide it into columns and rows.  At one point we got to 3 columns.  Looking at it, we figured we had to solve 3 x ? = 15.  Alexander C.'s hand shot up and he realized 3 x 5 =15, which Maya pointed out was actually solved by division: 15 / 3 = 5.  So we drew 3 columns and 5 rows and tested the math by counting each box.  Delicious division!