# 2nd Grade Math: Unit 3

## We will use the term compose or regroup instead of 'trade'.

https://youtu.be/_nfptPv0nG0

## Disregard the word 'borrow' in the video instead we use the term regroup.... 'borrowing' misrepresents what is taking place.

https://youtu.be/IqmccJc1R38

## Regrouping ones and tens work mat

https://youtu.be/sqUXLxN9ycs
https://youtu.be/VrPPtEVTqjk
https://youtu.be/K_ItJ8yzGCA
Using crayons | Addition and subtraction within 100 | Early Math | Khan Academy

## place value, chart, part, number sentence, equation, algorithm, equals,subtract, whole, minus, is the same as, relationship, difference

Mrs. Ochoa's class has 337 Dream Box points. Mrs. Sander’s class has 179 less points than Mrs. Ochoa’s class. How many Dreambox points does Mrs. Sander's have?

Represent the number sentence using the place value names-PVC CHART

Represent the whole number using pictures (models) VM, base ten blocks and PV chart:

Write the algorithm/number sentence

Reinforce vocabulary-label and discussions

Use terms: regroup ....not borrow...

## All lessons:

Whole Group:

Virtual Manipulatives

Pictorial

Number Sentence(s)

Small Group:

Place Value Mats

Base Ten Blocks/materials

Math Journal/Recording sheet( min. twice a week)

Solution statement

Focus: Expose your students to at least TWO different methods for subtraction

Number Line, Place Value Chart, OR Traditional Algorithm w/pictorial

The goal is to to allow students to develop a deeper understanding of the concept.

## Write a math story to go with the number sentence

Additional Small Group activities for the unit are in the Unit Documents (Schoology-second grade group)...use for small groups

Discussion, Turn and Talk, journal/recording sheet entries..

## Think Central Manipulatives

Use Think Central's virtual manipulatives as well...for regrouping, etc...

Sander's share

## Break a Hundred (MIF Book)-Lesson Three-Subtraction with Regrouping Ones and Tens

Break a Hundred! (Same materials as Make a Hundred!) Students will start at a hundred with 9 tens and 10 units, roll the die and subtract (remove) that amount from a hundred. The first one to get to zero or closest to zero wins!

## Lesson One: Subtraction without Regrouping

In whole and small groups always start with a story. Conceal the numbers so that students may focus on the math story and improve on their comprehension. Give students the opportunity to turn and talk about what they have read and understand of the story.

Ask questions: What do we know about the story? (some fish are orange, some are not...)

## Reveal the numbers..

After you reveal the numbers, read the story again and once again ask students to turn and talk what they understand about the story now.

Ask questions: What do we know? ( We know how many fish are in the pond and how many are orange) How many are orange? What are some colors the other fish could be? (red, blue. black,etc) How can we find how many are not orange?

Subtract, take away, less ____

Write the title' Subtraction without Regrouping'

Create anchor chart/SB copy with students, anchor chart should include:

• Place Value Chart-Students share how to make the chart
• Pictorial-students volunteers can come up and draw the base tens/Virtual maipulatives, Base Ten Blocks
• Number sentence/Number Bond/Bar Model-at least one or all three
• vocabulary words-label
• Solution statement-students turn and talk and share the statement.

## Friends of Ten

We created the anchor chart you see by using two-color counters on a ten frame. We put out ten red counters and I asked the students how many yellows we would need to put on our ten frame to make ten. Zero. We added 10 and 0 to our chart and wrote the equation, 10 + 0 = 10. We cleared the board and put out nine red counters. How many yellows to make 10? The students put out one yellow counter to show that it would take one more to make ten. We added 9 and 1 to the anchor chart. We continued this process until we had all the “friends”. I drew the “rainbow” to show the connections in the equations. Lots of oohs and ahs. First graders are easily amused.