Lesson objective: Find equivalent but easier problems for math facts using "doubles +1" and "doubles -1" strategies.

This lesson helps to build fluency in adding and subtracting numbers to 20 by having students create equivalent but easier sums using "doubles +1" and "doubles -1." Snap cubes are used here because it supports the idea of decomposing and composing addends to create the equivalent sums. This work develops students' understanding that we can use addition and subtraction facts we already know to help us solve new or challenging addition and subtraction problems.

Students engage in Mathematical Practice #8 (Look for and express regularity in repeated reasoning) as they decompose and compose numbers to create equivalent but easier sums. Students play *Double Links* using snap cubes and *Jumping Doubles* using number lines to create equivalent sums using a concrete and pictorial approach.

**Key vocabulary:**

- equivalent problems (sums)

**Special materials needed:**

- snap cubes
- dot cubes or number cubes
- action cards, recording sheet, number line template, action spinner (see game)