The purpose of this activity is for students to make sense of and solve Add To and Take From, Change Unknown story problems in a way that makes sense to them. Students represent the method they used and different methods are discussed during the Activity Synthesis. When students connect the quantities and action in each story problem to an equation and then solve the problem, they reason abstractly and quantitatively (MP2).

The teacher may want to incorporate movement into this activity by writing each problem on a piece of chart paper and placing each one in a different location around the classroom. Students can solve the problem at one location, discuss the problem with their partner, then move on to a new problem at a new location.

• Invite previously identified students to share.
• “How does help us find the number of penguins that went back into the water?” (If you start with all the penguins and take away the 5 that are still sitting on the rock, you will find out how many went back into the water.)

The purpose of this activity is for students to consider different ways to solve for the unknown in a Take From, Change Unknown problem. Students are presented with an equation that represents the order of the actions in the story. However, students often find that this equation is less intuitive to find the unknown value than an addition equation with an unknown addend. Students may also share the ways they use known sums and differences and how they make a 10 to find the unknown number.

In this activity, students show their understanding of the relationship between the quantities in the problem and their understanding of the relationship between addition and subtraction to share ways to solve the problem (MP2, MP7).

• Invite previously identified students to share.
• “How do you decide if you are going to add or subtract to find the unknown number in an equation?” (I usually subtract because I know what number to subtract, but I don't know what numbers to add. I always add because I like it better. I saw there was a 9, so I just thought about adding, because I know I can make a ten and add some more.)