Problem solving can be a real struggle.  Struggle is not a comfortable feeling, but it is where a lot of learning can happen.  When we struggle we need to embrace the “not knowing” and explore some ways to figure it out.  We know we have lots of strategies!

Today in grade 10 the problem was all about milk and cream.  Imagine you needed 1000mL of 2% milk for a recipe, and you didn’t have any.  You do have 2L of 1% milk and a carton of whipping cream (35%). Can you possibly create 2% milk?

After discussing the easy solution of “just go to the store”, we dug in a bit more.

We used logic

We wrote what we know, and thought about proportions and fractions

We made other equations (using decimal representations of percents)

One group got pretty close with an estimate (we need more than 900mL of 1%).

Eventually we made 2 equations and practiced substitution and elimination, and verified with desmos.  We’d need 970.6mL of 1% and 29.4mL of whipping cream to make 1L of 2% milk.

Some classmates wondered when you’d ever need to make 2% milk.  This question can apply to any kind of concentration problem, many you’ll see in chemistry next year.