In this unit, students build on their understanding of adding and subtracting within 20 to develop strategies for adding larger numbers. Students are also introduced to mentally adding 10. Students will use various strategies and representations, including concrete manipulatives, drawings, and numerical representations to add 10 more to a number and combine 2digit numbers. Students may count on by ten from one number, decompose numbers into tens and ones and then combine like values, or combine ones to compose a new ten. Developing various efficient strategies for adding multiples of ten and the discussions in terms of tens and ones will continue to build studentsâ€™ number sense and place value fluency.
Key Concepts:
 We can find 10 more than a twodigit number without having to count, by adding a ten.
 We can add twodigit numbers by adding tens to tens and ones to ones.
 When adding twodigit numbers, we can compose a new ten from ones.
Prior Knowledge Needed:
 Composing ten; Grade K, Unit 12, K.OA.A.4
 Understanding ten ones make a ten; Grade 1, Unit 1, 1.NBT.B.2
 Using place value to read, write, represent, and compare numbers; Grade 1, Unit 8, 1.NBT.B.2
 Developing addition and subtraction strategies; Grade 1, Unit 6, 1.OA.A.1
Units on the Horizon:
 Using understanding of place value to add and subtract; Grade 1, Unit 14
 Relating skip counting to mental addition and subtraction; Grade 2, Unit 8
 Understanding threedigit numbers; Grade 2, Unit 6
Lessons

Lesson objective: Students will be able to add 10 to any 2digit number without having to count on by ones. Students bring prior knowledge of adding on to a number from K.CC.A.2. This prior knowledge is extended to adding on 10 more as students figure o...

Lesson objective: Students will be able to fluently add ten to a 2digit number. This lesson helps to build fluency with adding 10. Cubes and hundred charts are used here because students can access a concrete or abstract representation. This work devel...

Lesson objective: Students will be able to apply what they know about adding ten more to find combinations that are 10 numbers apart. This lesson provides an opportunity for students to apply their knowledge and understanding of adding 10 more to a math...

Lesson objective: Students will be able to add a twodigit number with a multiple of ten by adding tens with tens and ones with ones. Students bring prior knowledge of place value from 1.NBT.B.2. This prior knowledge is extended to adding twodigit numb...

Lesson objective: Add a twodigit number and a multiple of ten by adding tens with tens and ones with ones. This lesson helps to build procedural skill with decomposing numbers into tens and ones to add. Cubes and numbers are used here because they supp...

Lesson objective: Students will be able to apply what they know about using place value to add a twodigit number to a multiple of ten. This lesson provides an opportunity for students to apply their knowledge and understanding of adding a twodigit num...

Lesson objective: Students will be able to compose a ten when adding a twodigit number to a onedigit number. Students bring prior knowledge of decomposing numbers up to ten from K.OA.A.3. This prior knowledge is extended to composing a ten as students...

Lesson objective: Add a twodigit number with a onedigit number, sometimes composing a ten. This lesson helps to build fluency with composing a new ten. Cubes are used here because students will be able to see that a new ten is "complete." This work de...

Lesson objective: Add a twodigit number with a onedigit number, sometimes composing a ten. This lesson helps to build fluency with addition. Cubes and written notation are used here to support students' need to concrete representation, but also suppor...

Lesson objective: Students will be able to apply what they know about missing addend problems and composing a new ten to solve for missing numbers. This lesson provides an opportunity for students to apply their knowledge and understanding of composing ...