How Many More?

Second graders are expected to fluently add and subtract within 20 using mental strategies by the end of second grade according to the Common Core Standard.  The use of manipulatives helps a lot with developing a scholar's mental strategies.  Here we used Rekenreks to help build numbers to 20.

In this activity, students rolled a  1-20 die and had to figure out what went with their number to make 20.

We tried dice that had the numbers 1-20, then we used 1-12.  Each time students could use the rekenrek to help them build the number on their die and then see what number they needed to go with 20.

  Once they became a little fluent with this we challenged ourselves by figuring out what numbers we would need for combinations to 100.  Another one of our standards.  Students used place value dice 0-90 to figure out what they would start with.  Then we used the large rekenrek to figure out what we needed to equal 100 as shown in the picture below.