Decomposing (breaking apart) and recomposing (combining parts) strategies may be used in two ways as
shown in the example above. One strategy is to decompose addends and add by place value. The other is to
make friendly numbers (like 10, 20,30....). Study the example above to help you answer the following
questions.

Dan, a second-grade teacher, is modeling how students might solve the following problems using a number line. For (a) and (b), show how he can model each problem below by decomposing the second addend by place value.


b) 79 +21

c) Imani likes to use "friendly numbers" when she adds. Model how she might solve 48 + 29 on a number line
using this idea.