# ALEX Lesson Plan

## Three-Digit Subtraction

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This lesson provided by:
 Author: Emilie Workman System: Baldwin County School: Swift Elementary School
General Lesson Information
 Lesson Plan ID: 9484 Title: Three-Digit Subtraction Overview/Annotation: This lesson uses technology and literature to teach subtraction of three-digit numbers, including subtraction across zeros.
Associated Standards and Objectives
Content Standard(s):
 MA2015 (3) 11. 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. [3-NBT2] MA2015 (4) 9. Fluently add and subtract multi-digit whole numbers using the standard algorithm. [4-NBT4]

Local/National Standards:

Primary Learning Objective(s):

Students will subtract three-digit numbers from three-digit numbers.

Students will access a given website and print material from that website. Students will use desktop publishing software to create a book.

Preparation Information
 Total Duration: Greater than 120 Minutes Materials and Resources: Overhead projector, base ten blocks (such as Unifix cubes) for overhead, base ten blocks for use as manipulatives, Shark Swimathon by Stuart J.Murphy, three dice, white boards and erasable markers for each student, calculators (optional) Technology Resources Needed: Computers with Internet access, printer, desktop publishing/word processing software Background/Preparation: Students should be proficient in subtracting two-digit numbers with regrouping. If the teacher needs ideas for teaching regrouping with the use of base ten blocks he/she can visit this site for an overview http://www.eduplace.com/math/mw/background/2/12/te_2_12_overview.html.
Procedures/Activities:
 1.)Read Shark Swimathon by Stuart J. Murphy. (Overview: The Ocean City Sharks have to swim 75 laps by the end of the week, and every day they figure out how many laps are left to go. Swimming and subtraction are all part of the fun!) During the reading, pause and instruct students to compute the math problems from the book on dry erase boards or paper. Another option is to have half of the students use calculators to compute the problems, if this is a skill that has been introduced previously, and compare answers at the end of the book. (This is a two-digit subtraction book that will review skills prior to the introduction of three-digit subtraction.) 2.)Give a number description orally and instruct students to write the three-digit number described on their dry erase boards or paper. Example: What number has 6 hundreds, no tens, and no ones? (600) Brainstorm other ways to depict the same number. Example: 5 hundreds, 10 tens and no ones OR 4 hundreds, 10 tens and 100 ones, etc. 3.)Using base ten blocks (unifix cubes) made for overhead projectors, model the subtraction of 175 from 600. An alternaive is to use the following link to an interactive site that uses base ten blocks to depict subtraction problems. Regardless of the method chosen, model regrouping across zeros. Complete several practice problems, then have students work in small groups with manipulatives to solve three-digit subtraction problems. Allow individual practice either at the overhead or on the website.(Virtual Manipulative: Base Block Subtraction)Click on "Create a Problem". 4.)After adequate practice with the base ten blocks students will practice computing three-digit subtraction problems. Roll three dice to arrive at a three-digit number. Record the number. Roll the dice again to arrive at a second three-digit number. Students should determine which number is larger and create a subtraction problem using the two numbers. Students will compute the problem on dry erase boards and reveal their work to the teacher. A nod or thumbs up can be given to students with correct answers. Depending on time students can play the dice game in small groups.(Welcome to WebDice!)This site may be used it you are short on dice. 5.)Instruct students to use classroom computers to access the following website, print the worksheet, and complete the math problems independently.(Three-Digit Subtraction with Regrouping) 6.)As a cummulative project assign groups of students to work together to write a story similar to Shark Swimathon that involves three-digit math problems as part of the story. As an alternative write a story as a large group. Use desktop publishing/word processing software to create a finished product. Books can then become a part of the classroom math library.
Assessment
 Assessment Strategies Teacher will assess students through observation of their work on the dry erase boards and by checking their work on the worksheet printed in Step 5.
 Acceleration: Students who are already proficient at three-digit subtraction may work together and create a book similar to Shark Swimathon that involves three-digit subtraction. The students should provide a guide to the book that includes computation of the math problems. Intervention: Teachers can access the following site and customize worksheets for individual students who require extra practice: http://www.aplusmath.com/Worksheets/Subtraction.html.

Each area below is a direct link to general teaching strategies/classroom accommodations for students with identified learning and/or behavior problems such as: reading or math performance below grade level; test or classroom assignments/quizzes at a failing level; failure to complete assignments independently; difficulty with short-term memory, abstract concepts, staying on task, or following directions; poor peer interaction or temper tantrums, and other learning or behavior problems.

 Presentation of Material Environment Time Demands Materials Attention Using Groups and Peers Assisting the Reluctant Starter Dealing with Inappropriate Behavior
Be sure to check the student's IEP for specific accommodations.