Change Unknown Problem 1 with Child 5 (Early Math Collaborative)
View more in our Early Math Idea Library: https://earlymath.erikson.edu/ideas
This second grader uses derived facts to solve a problem fluently. Just one example of mental math strategies used by elementary students.
Focus on the Child videos are taken from one-on-one interviews with individual children. The interviews are designed to elicit evidence of children’s mathematical thinking. They are not teaching episodes or formal assessments.
Why is this important?
Double facts are easy for most children to remember. Here, a second grade student uses 8+8 to mentally find a missing addend: 8 + ? = 15. This is a good example of computational fluency.
BIG IDEA:
Sets can be changed by adding items (joining) or by taking some away (separating).
Many problem situations involve change—adding to or taking away from a set. Such changes lend themselves to concrete models or to acting out as sets are joined or separated and then counted to find out “how many now?”. However, it is also important for young children to make the more foundational generalization that adding increases and taking away decreases the quantity in a set.
FOUNDATIONAL MATH TOPIC: NUMBER OPERATIONS
When children focus on what happens when we join two sets together or separate a set into parts, they learn about how quantities change. When they have lots of experience comparing amounts, they become familiar with thinking about differences between sets. And when they have opportunities to see how a single large set can be composed of two or more smaller sets, they get comfortable with the fact that larger numbers contain smaller numbers. These ways of mentally modeling real situations are what we mean by number operations.