Before You Begin this Unit… 

Unit at a Glance 
By the end of 2^{nd} grade, students should have mastered addition combinations to 20. You may want to assess the combinations they know using the Hiding Assessment. Read session 2.1 and use this lesson as a minilesson. This unit highlights the structure of our base ten system as students add and subtract using strips and singles, pennies, dimes, and dollars.   Making tens   Making tens of tens The standard algorithm is not introduced in 3^{rd} grade. Read the following quote from the "Read more here" link and other article below to find out why... "Most (but not all) children will, with extensive practice, eventually learn to use traditional algorithms with some competence. This skill often comes at too great a price: students learn to ignore their own reasoning in favour of following rules." Look at this article about understanding of our place value system. Read more here. Although the work in this unit has students adding and subtracting to 100, students will get experience with larger numbers later (3.NBT.2). 
Suggested Dates:
Estimated Duration: 16 lessons *Investigation 1: 9 lessons *Session 1.1 OMIT the “What’s the Temperature” 

Standards Addressed in the Unit  
3.OA.8 Solve twostep word problems using the four operations. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding. 3.OA.9 Identify arithmetic patterns (including patterns in the addition table or multiplication table), and explain them using properties of operations. 3.NBT.2 Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction. Link to CCSS Unpacking DocumentUpdated Sept. '15 (Look at pages 1620) 