Getting Better At Addition and Subtraction Final Project

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SWBAT use what they know about addition and subtraction to solve a problem.

Big Idea

Building fluency with addition and subtraction is one of the Common Core Critical Areas for 2nd grade.

Creating a Real Life Situation with Math

35 minutes

Students have been working with addition and subtraction during this unit. They have worked with understanding word problem questions, modeling their work, checking their own work and writing math problems both horizontally and vertically. Today I want students to incorporate all of these things into the creation of a special product presentation. I am creating a curriculum embedded assessment.

During several writing blocks students invented a machine to solve a problem they have in winter. They might make a mitten drier, or a flying sled to get them back up a hill, etc. They made drawings, labeled the drawings, and thought about what materials they would make their invention out of. 

I explain that beginning today we will work through several steps for them to sell the product that they invented in a writing process.   They will be writing and solving the math problems that will show how much money they made in selling their object. I show students the worksheet they will be working with.Assessment Project Worksheet

I begin by having everyone write the name of their object on their papers and listing the things it will be made out of.  Next I ask them to think of the 2 most important materials they will use and to write them down on the next set of lines (I have a copy on the Smart Board so I can model for students what I want them to do.) Now I ask them to fill in how many pieces of each they will need. I say, "Ok, you are planning to buy3 pieces of something at $2.00 for each piece, how much would that be in all?" ($6.00) How did you figure that out? (counted by 2s, counted on my number line, counted on my number grid). Students are reasoning abstractly and quantitatively here as they figure out how much they will spend to build their object MP2)

OK, now you need to figure out the total for each thing you will buy remembering that each piece costs $2.00 as we just did together and write a number sentence to help you find the total you will spend to build 1 of your inventions. I write 2 + 2 + 2 = 6 on the line on my model. I circulate around the room to look at the number models students are creating. (MP4). 

I tell students that we will finish this part today by figuring out how much they would have left from their $100 if they built one of their inventions at the cost they just discovered. I fill in the rest of my page and then ask students to do the same. 


Day 2 Selling Our Product

45 minutes

Today I return the math worksheets and invention drawings to students I tell  students that today they will make an advertisement for their product which gives the price in dollars. Students have not had the experience of subtracting dollars and cents at this point so we limit the price to even dollars. I remind students that even dollars are like Smiley Face numbers because the change is zero zero.

I give students about 20 minutes to complete their advertiesments.

I ring the bell and ask students to stop drawing, even if they are not quite done they may finish their ads for morning work (at arrival time my class has about 15 minutes before everyone is in the room and this time is used for finishing up work from the day before). I ask them to think of how many of their objects they wish to sell (a number between 1 and 5) and record it at the top of the second page of the math worksheet along with the price they decided on and put on their poster/advertisement. 

Ok now if you were to sell all of your inventions at your price how much money would you make? Here we need to see if we can figure this out (make sense of the problem and solve it MP1) I ask for suggestions of what we might do. (I am expected students to suggest adding the price as many times as the number of items, using repeated addition.) I model writing a repeated addition sentence for my example and ask students what strategy they might now use to solve the problem? (Students suggest number grid, number line, tally marks, counting by 5,10 etc.) Together we solve my problem and then I ask them to try to write their own problems. I circulate around to help students who may be struggling. Students who finish quickly can work on their advertisements. 

Next, to figure out their profit (anything beyond the initial $100 that they "owe" to me) students, students must structure the problem using either addition and subtraction strategies. Again I model finding the amounts for the money I made (on page 2) and the money I had left (on page 1). I ask for a number model that will tell me how much money I have. I ask students to fill in and solve their number model (MP4).  I expect students to employ the use of their number line or number grid, or to rewrite the problem in columns, or add the tens and the ones to get their answer. 

Ok, Now we will see how much money you made. Remember you bought the pieces of material for $100.00? Well you have to pay that back, because I lent you the $100.00, so I am going to give you the amount of money you made in all, and I am going to ask you to take out the money that you spent (from page one), and then count to see how much you have in all. To make this go more quickly, I place tens and ones on each table. I ask students to tell a partner how much they made and the partner will count out that amount of money. The student receiving the money can check for accuracy. 

I know that they really only paid for 1 of the objects, but that is another step that I have chosen to ignore because the objective is for students to see how they can use money and model with mathematics to solve a series of related questions. Because it is a performance assessment I am also interested in the accuracy of their use of strategies Choosing an addition strategy to solve complex addition sentences for numbers under 100. 

I ask students to count all their money, take out the 100 they owe me and see what their profit is. They then write a math sentence to show how much money they made.

Finally students write the "smiley face" number (estimation) to show their profit to the class.



20 minutes

I bring students to the rug to close this assessment. I ask them to bring their advertisements and their profit. I record the profit numbers on the board. Together we find the greatest and the least profit. I ask students if we can find a way to find the difference between the 2. I let several students how they would find the difference between the least and the greatest profits. 

Finally I tell students that they will all have a chance to share their cool inventions. I tell students that as they listen they should think about whether this invention is one they would like. They can pretend to buy as many of the inventions as they would like. I tell them to remember that they are thinking about the invention not about whether the maker was a friend or not.  I ask each student to share his/her invention. After they share I praise the inventor for solving a problem with…. and then ask for a thumbs up if other students think they might like to buy such an invention. This is a great way to build pride in the effort that students have put into this project because students get excited about the fun inventions of their classmates. Each student has had a chance to share his/her invention with us. 

I do honor a student's wish not to share at this time. If a student is uncomfortable sharing I do not force them to do so. I honor their invention as well as their feelings. I ask if I can share it or not, and then do as they ask. Some students are not proud of their inventions and should not be forced to share. With these students, I take them aside later and praise the pieces I feel show their hard work, and ask them what they might have done differently if they were to change it. I give them private praise for their effort.