Adding and Subtracting 10 Unit of Study 9: Two Digit Addition and Subtraction Global Concept Guide: 1 of 3

Content Development  As students begin adding tens, some may still need to use manipulatives before drawing quick pictures.  Encourage students to develop their own strategies for adding tens. Let students describe their strategies without being interrupted or corrected. Many times students will discover their own mistakes if allowed to think through their idea.  Open Number Lines are a great tool. Allow students to choose the intervals.

Day 1  Use problems that encourage students to justify their thinking with manipulatives, pictures, number lines, hundreds charts, ten frames etc… (For Example: Mrs. James sharpens 30 pencils. If 10 students borrow a pencil, how many pencils does Mrs. James have left?)  Go Math Lesson 8.3 focuses on adding tens Example: Use a Hundreds Chart to Model the number sentence 10+20

Day 2  Secret Number Game- Tell your students that you have a secret number. Then give them clues to help them guess your number, such as “This number is 20 more than 30 and 20 less than 70.” You may want to give students a hundred chart to help them solve. Have students prove their answer using a hundreds chart or other manipulative. Extend by having students create their own secret number and have partners or classmates guess.  Go Math Lesson 8.3 focuses on subtraction of tens

Day 3  Possible Engage: I Have, Who Has? Activity- Have numeral cards cut out and in a container or hat (Start with tens first 10, 20, 30, 40, etc.) Students will randomly choose a number or numbers. The first volunteer will state “I have ____, who has ten more or ten less? Students with one of those numbers will respond with what their number is and prove how they know it is ten more or ten less using a hundreds chart, number line, manipulatives etc…  Adding sets of 10- This activity utilizes Base Ten Blocks to see patterns when adding tens. Adding sets of 10  Open number lines help students internalize the patterns they have observed when adding and subtracting with ten. The purpose of the open number line is to allow students to choose their own intervals; therefore there will be more than one acceptable representation. This is a great opportunity for student discussion.

Day 4  Possible Engage: I Have, Who Has? activity. Same activity as day 3 but move on to numbers with values in the ones place, such as 11, 29, 36, etc.)  Sam’s Base Ten Blocks- This activity utilizes Base Ten Blocks to help students see patterns when subtracting tens Sam’s Base Ten Blocks  Continue the use of open number lines

Enrich/Reteach/Intervention Enrich: Go Math Grade 1 Enrich 8.2 (p.E62) Go Math Grade 1 Enrich 8.2 (p.E63) Intervention/Small Group: Go Math Grade 1 Tier 2 Intervention activity- perfect for small group (TE p. 325B) Go Math Grade 1 Reteach 8.3 (p. R63) Soar to Success Activity 11.18

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