The purpose of this activity is for students to add a one-digit number and a two-digit number in a way that makes sense to them. 

Monitor for and select students with the following approaches to share in the Activity Synthesis:

• Start with 47, and then count on 8. 
• Start with 47, decompose the 8 into 3 and 5, make a new ten with 47 and 3, and then add the remaining 5. 
• Decompose 47 into 4 tens and 7 ones, add the ones, and then add the 4 tens. 

The approaches are sequenced from more concrete to more abstract to help students make sense of different approaches when it is possible to compose a new ten. Aim to elicit both key mathematical ideas and a variety of student voices, especially students who haven't shared recently

During the Activity Synthesis, the teacher represents student approaches with connecting cubes, so the new ten is visible to all students. 

• Invite previously selected students to share in the given order. Record or display their work for all to see.
• If students only share equations or the counting sequence, show each approach with connecting cubes.
• Connect students’ approaches by asking:
  • “¿En qué se parecen los métodos? ¿En qué son diferentes?“ // “How are the methods alike? How are they different?” (They all got 55. The first one started at 47 and counted on by ones. The second one added 3 to 47 to make 50 and then added the 5 ones. The last one added the ones first and then added the tens.)
• If no students mentions making a ten, display the second approach and connect it to the learning goal by asking,
  • “¿Cómo ____ mostró que se formó una nueva decena?“ // “How did _____ show that they made a new ten?” (They broke 8 apart so they could use 3 ones to make a ten with the 7 ones in 47. When they added 3 more ones to the 7 ones in 47, they could see that they made a new tower of 10.)

The purpose of this activity is for students to practice adding a one-digit number and a two-digit number in a way that makes sense to them. Students may choose to use methods shared in the previous activity. Give half of the class one-digit numbers and the other half two-digit numbers. Students work in pairs to create a sum with a two-digit number and a one-digit number. In some problems, the sum will require composing a ten when adding ones to ones. Monitor for students who share ways they make a new ten with connecting cubes or drawings to share in the Activity Synthesis.

When students choose a method to add based on the pair of numbers they are adding, they make use of structure and apply regularity in reasoning (MP7, MP8). This could mean counting on when the one-digit number is small, adding the ones when there is no new ten, and adding on to make a ten if needed.

• Invite previously identified students to share.
• After each student shares, ask “¿Por qué escogiste este método?” // “Why did you choose this method?” (Since I was adding only 3, I could count on quickly. The number 9 would take too long to count on, so I broke it apart to make a new ten and then added the rest.)

The purpose of this activity is for students to solve story problems that require adding a two-digit number and a one-digit number with composing a ten. This activity offers additional practice using methods discussed in the previous activities, while giving context for adding these quantities. Students share examples of when they have added or seen others add quantities like those they have been adding. This activity is optional because it provides practice solving story problems with numbers larger than 20, which is not an expectation of students in grade 1. 

• Invite previously identified students to share their method for each problem.