Lesson Data:

Diana L. Sammis

Second Grade

Subtraction of double digit numbers using tens

 

Overview The second graders will be taught how to subtract double digit numbers using tens.  I will show how these same numbers can be subtracted just like one digit numbers when the zero is removed.  Different activities will be used to show them the mechanics of subtraction.  It is important for them to understand subtraction because it a required skill for the real world.

Goal:  Students will understand mathematics and become mathematically confident by communicating and reasoning mathematically, by applying mathematics in real-world settings, and by solving problems through the study of numbers and their operations.

 

Standards:

Number and Operations Standard for Grades Pre-K–2

Students will understand numbers, ways of representing numbers, relationships among numbers, and number systems, understand meanings of operations and how they relate to one another and compute fluently and make reasonable estimates

MST Standard 3:   Mathematics Students will understand mathematics and become mathematically confident by communicating and reasoning mathematically, by applying mathematics in real-world settings, and by solving problems through the integrated study of number systems, geometry, algebra, data analysis, probability, and trigonometry.

Key Idea: Students use mathematical operations and relationships among them to understand mathematics.

Performance Indicator:  Students will add, subtract, multiply, and divide whole numbers.

Independent Practice:

Objective: 

               Given a worksheet with 10 subtraction problems, students will use the assignment to practice their subtraction skills by using information, methods, concepts, theories in new situations to solve problems using required skills or knowledge and calculate subtraction problems with tens and two digits  and complete 7 out of the 10 problems correctly.

             

 

     Materials Needed:  Worksheet with 10 subtraction problems containing 2 digits and that are in tens.

Formative Assessment:  After correcting all students’ sheets, the teacher can gauge how well students are comprehending the material.

 

ELA Standard 1:  Students will listen, speak, read, and write for information and                                          understanding.

 

Performance Indicator:  Students will write mathematical problems including word                                                problems that include relevant information and exclude                                                                                 extraneous material.

SS National Standard:

How to Analyze the Spatial Organization of People, Places, and Environments on Earth’s Surface

SS Standard 3:   Geography Students will use a variety of intellectual skills to demonstrate their understanding of the geography of the interdependent world in which we live—local, national, and global—including the distribution of people, places, and environments over the Earth’s surface.

Performance Indicators:  Students will locate the earth’s continents in relation to each other and to principal parallels and meridians.

Performance Indicators:  Students will ask geographic questions about locations and how these locations are related to the locations of other people and places.

UNIFYING CONCEPTS AND PROCESSES STANDARD

Conceptual and procedural schemes unify science disciplines and provide students with powerful ideas to help them understand the natural world. Because of the underlying principles embodied in this standard, the understandings and abilities described here are repeated in the other content standards. Unifying concepts and processes include

·         Systems, order, and organization.

 Science Standard Physical Setting:  Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.

Performance Indicator: Students will describe patterns of daily, monthly, and seasonal changes in their environment.

Objective:

                        Given two numbers that represent different temperatures of different locations throughout the world, the student will calculate and write down the answers to ten problems resulting in the differences of 10 sets of temperatures and will complete 7 out of 10 problems and attempt to have correct 7 out of 10 problems

        

Materials:   Globe of the World

                   Chalk or Dry Erase markers for writing the temperatures on board

                   Blackboard, chalk board or dry erase board for recording temperatures

                   Paper for students to write their answers

TIP:   Make sure that temperatures are in tens.  (20°-10°=  ___ )

To allow the students to feel comfortable, go through several temperature sets to ensure that the students really understand the one’s place rule and also how subtraction works.  Speeding up the process progressively, choose students who previously did not reach the right answer and have them answer a few temperature problems in a row.  This repetition will build confidence and allow them to feel comfortable with the material.

Formative Assessment:  One student will come up to the board and pick out a location on the globe.  A second student will pick out a second location and write its temperature on the board.  A third student will come up and figure out the difference between the two temperatures. A complete rotation will occur to make sure all students know how to subtract and those who do not will continue to pick out locations, some that are exotic to pique their interest and continue with the subtraction problems.

Anticipatory Set:  

A story about dolphins swimming in a pool will be told.  A magnetic board with dolphins swimming around in the pool will be displayed.  Each time 10 dolphins will see a fish and jump out of the pool into the ocean.  Each time this happens, students will be asked to count as a class how many dolphins are left together in the pool. 

STORY:  50 Dolphins were in the pool at Sea World.  10 jumped out when they saw some scrumptious fish in the ocean.  How many are left?  Let’s count them together.  10 more jumped out when they saw scrumptious fish in the ocean.  How many are left and so on…  

At the end of the exercise, explain how each time 10 dolphins leaped out of the pool, there were ten less.  Explain that this process is called subtraction.  

 

Objective and Purpose of Lesson:  For second graders, it’s important for you to know how to subtract.  When you buy candy in a store or you buy lunch at school, sometimes the cashier can make mistakes and give you the wrong change.  If you know how to subtract, you can remember how much money the food or candy cost, pay for it and then see if the returned change is the correct amount.

That is what we’re going to learn about to day.  We’re going to learn about subtraction using tens. 

GUIDED PRACTICE

After the Anticipatory set is completed, some drill and practice should be used to really bring home the operation of subtraction. 

Subtraction problems will be placed on the board and students will be asked to come up to the board to solve each problem.  Also, I will say loudly a few subtraction problems and field responses from the second graders to see where everyone is at with learning the skill.  The key principle for them to learn will be to drop the 0 to make finding the answer easier.

If any student is not able to solve at least 7 of these subtraction problems, accommodate that student by sitting with and showing them the one’s place rule which should also be modeled at the beginning of the lesson.  If other students have excelled at this skill, they too can show the students who are having problems how to use the skill  They can also begin to read some books set aside for them about subtraction.  These books include stories about animals and people being bigger than one another by a certain amount and helps conceptualize subtraction..

            One’s Place Rule:         60               6          

-         40            - 4

20                              2

 With this rule the only difference between these two problems is the presence of the 0.

 

Also, “manipulatives” may also be used to visually show learners how to subtract using tens and two digit numbers.  Plastic bars that have been segmented into ten parts can be used to show how when a certain number of units are taken away from another number, an answer is reached. Formative Assessment:  Each student will be given a worksheet with subtraction problems.  They will use the rods to solve for the answers to each problem.   Based on how well the students do on each of these problems, the teacher can go back over the lesson.

Diagnostic Assessment:   Software that generates a quiz with 20 subtraction problems can be used to test the abilities of the students.  The results can be electronically relayed back to the teacher as well as the student and inform both teacher and student of deficits in skill and ability.

 Homework

Tell students to accompany their parents to the grocery store.  Have them place 20 oranges in a scale in the produce section.  Then ask them to count the remaining oranges.

Send students home with a worksheet that has several ideas on it.  Each idea should have materials that a normal household would have.  Each activity should discuss subtraction and how one thing is bigger than the other.  Some of the activities could involve dinner time.  Have their parents serve them 30 green beans and have them eat 10 and count the remaining beans.

Closure

Summative Evaluation Tool

A test will be given with several types of subtraction problems.  5 of the problems will involve simply using subtraction to solve double digit tens problems.

Then next five questions will involve use of the rods to solve for each subtraction problem.

The next five questions will involve animals or people in the problems to solve the answers.

The next five questions will use the removal of the 0 to figure out the answer to each question.

With a total of 20 questions a passing grade will include getting 15 correct.