Mathematics Grade 2
Strand: OPERATIONS AND ALGEBRAIC THINKING (2.OA) Standard 2.OA.1
Mathematics Grade 2
Strand: NUMBER AND OPERATIONS IN BASE TEN (2.NBT) Standard 2.NBT.7
Mathematics Grade 2
Strand: NUMBER AND OPERATIONS IN BASE TEN (2.NBT) Standard 2.NBT.9
Students will develop a number sense through recognition and practice with benchmark numbers.
What Makes 10?
Close to 100
Salute!
Additional Resources
Books
Individuals
Additional Media
Students need to develop number sense through recognition and practice with benchmark numbers. Having a firm understanding of tens and hundreds will help students be more skilled in both addition and subtraction. It will help them see the relationships between the four operations. It will also help them to become mathematical problem solvers, and to understand how and why numbers and math work as they do.
1. Demonstrate a positive learning attitude toward mathematics.
2. Become mathematical problem solvers.
3. Reason mathematically.
Invitation to Learn
Read The Magic School Bus Gets Ants In Its Pants aloud to the
class.
Scatter 100 plastic ants on the floor or desks in the classroom. Instruct students to hurry and get them all! They can’t leave one ant on the floor or soon there will be thousands of ants invading the classroom!
Have each student gather some ants, then take them back to their desks and carefully count how many they have. Tell them that you know there were 100 ants originally. Students must figure out how they can tell if they have really gotten them all. Hopefully, they will come up with the idea that they can put together all their groups of ants and find a total.
Journaling: Students record the ideas in their journals.
Instructional Procedures
Complete the next three activities to reinforce number sense with benchmark numbers.
What Makes 10
Sample problem 1: Place 5 blocks on the mat, ask “What makes 10?” Have students give answers out loud, and then prove their answers by continuing to place blocks on the mat until all the spaces are filled up. Continue doing this and expand it to make multiples of 10.
Sample problem 2: Place 2 base ten sticks and 3 blocks on the mat. Have students predict what multiple of 10 they will have when they complete “What makes 10?”
Close to 100
Adapted from Investigations in Numbers, Data, and Space, by Dale
Seymour Publications.
Students play in pairs so you need one deck of cards for each pair of students. Each deck consists of 44 cards—four of each of the digits 0-9, plus four “wild cards.” Each individual player needs a Close to 100 Scoresheet.
The object of the game is to create two digit numbers whose sum is as close to 100 as possible. Each game consists of five rounds.
Salute!
This game can be adapted to play and practice with addition,
subtraction, or multiplication.
Example: Johnny holds up a 30 and Susie holds up a 9. The calculator announces 39. Johnny figures out that his card must be 30 since Susie’s is 9 and announces 30. He wins and collects both cards.
(Complete original words and music are available at: http://www.niehs.nih.gov/kids/lyrics/antsgo.htm)
To the tune of “The Ants Go Marching One by One”
Oh when we add we get them all, the sum, the sum
Oh when we add we get them all, the sum, the sum
Combine the addends and total them up
It works just fine if you mix them up
So when you add you must make sure you get them all
Add, Add, Add, Add, Add, Add, Add, Add!Do other sums with the song.
Example:
The ants go marching 30 by 30 Hurrah, hurrah
The ants go marching 30 by 30 Hurrah, hurrah
Let’s find which addends we can add up
To get the sum we must hurry up
And the ants go marching 30 by 30 by 30 by 30
add, add , add, add, add, add, add, add, add!
Family Connections
Send a letter home to families explaining the concepts you are
studying. Encourage families to go outside together and find an
ant colony to observe and make up problems about the ants as
they watch them.
Research Basis
Walsh, S. (2000). How To Add, Subtract, Multiply, and Divide Natural Numbers Online at http://faculty.ed.u,uc.edu/-swalsh/Math%20Articles/ASMD.html
This article explains the history of math and how the standard algorithms came into existence. It also explores the reasons why algorithms are important and the concept that before algorithms are taught, students need to have a thorough understanding of the process of the operation and how and why it works.
Raimi, R.A. (2002). On Algorithms of Arithmetic, Department of Mathematics, University of Rochester, Online at: www.nychold.org/raimi-algs0209.html
This article explores why students still need to learn to perform basic mathematical operations rather than relying solely on calculators. Raimi draws an interesting comparison between walking and driving a car. After cars were invented, people did not completely quit walking. People choose whether to walk or drive by doing what makes the most sense for the situation. He suggests that we teach students the same concept in math—use the method that makes the most sense.