Using Trial & Error

To support students learning to use trial and error provide students with concrete materials to solve part-part-whole (part unknown) problem types.  A sample problem from Lawson (pg. 72) is "There are 14 pieces of pizza left in the box. Eight pieces have pepperoni and the rest don’t.  How many pieces of pizza don’t have pepperoni?" Educators should also encourage reasoning and intentionality when using trial and error, instead of "guessing". Once students have an understanding of trial and error, educators should encourage more efficient strategies.