Students have shown proficiency in counting by 10s and 100s. Today I begin by having them count by 5s. I put the numbers 25 and 30 on the board followed by 3 blank spaces and ask them to complete the counts in their math journals. I have one student fill in the blanks on the board.
I ask students what are we counting by? I ask them if they can count by 5s above 100?
I say we will count out loud together. I start with 100, 105, and then try to withdraw my voice as I let students take the lead in saying the numbers. At 150 I stop them and praise their work.
Next I write 205, 210 on the board followed by 5 blank lines. I ask them to complete the counts in their math journals. I have a student write the counts on the board. We check together and look for patterns that they may notice. The may notice the changes in the tens digit such as 215, 220, 225, 230 where there are 2 of each digit in the tens place and then they change; they may see that the ones place goes to 0,5, 0 ,5; they may notice that the hundreds digit does not change at all, etc.
I tell students they are very good at counting by 5s. I ask them if they can count by 25s?
I start with 25 and ask what is next? Some students know that 50 is next. We work together to figure out 75 and then 100. We continue on to 200. I record the numbers on the board as the students say them. We stop and look at the pattern we have created with repeating numbers.
I sing students a silly song (more of a chant) that goes "25, 50, 75, a dollar. Everyone counting quarters stand up and holler!" We repeat it several times to help students remember the counts by 25.
I tell students that today they will work with money in small groups. I divide them into 3 groups and have them move to their center. I tell them that the directions are at the centers that are independent. I have chosen not to take the time to preview the centers because I do want to encourage independence among the students and know that the directions are ones that they should be able to follow on their own. They will need to read the directions and make sense of the problems or activities presented. (MP1).
Students will rotate through 3 math centers during the next 45 minutes. I have chosen to put the students in homogeneous groups so that I can vary the level of instruction at each center.
Center One: Here students will use coins to purchase items. They will have the chance to buy small toys (they return the toys at the end of the lesson). Students will count out the coins to pay for the item. I vary the price tags based on the group at the center. The students work in pairs with one child paying for the object and another counting the money to see if it is correct. Students take turns buying and selling
Center Two: I work with students at this center to make change. I use the large paper coins so that all children can see what we are doing. I show them an object and tell them it costs 23 cents. I tell them I only have a quarter. I bring out the balance scale and tell them that one side has the object and will need change to balance with my quarter. I ask the students to count from 23 to 25 using pennies. How many pennies would I need to make it balance? Students say 2. I know that the weights do not match with the scale so I use my hand to push down the quarter side to show that it is of greater value. Next we add the 2 pennies and now I can hold the scale even. The scale is a model that will help children grasp the idea that the object plus change should equal or balance the quarter that I pay with (MP4)
I repeat this activity making the difference between the quarter and the cost greater and greater. I encourage students to begin using nickels or dimes to complete the balance.
I move to making change from 50 cents for the students who already understand change from 25.
Center Three: Here students work independently on a practice page money 2 ways.docx that involves paying for an object 2 different ways. Students are expected to find 2 different coin combinations to pay for each object. They may use the plastic coins to help them with this activity or they can just draw the coins. They are used to drawing a circle with the P,N,D,Q written inside the circle to represent the coin. Students are expected to make sense of the problems on the page and persevere in solving them (MP1).
I have students clean up and return to their seats. I put a challenge problem on the board for them. I want to buy this book for 85 cents. I only have 1 dollar. What can I do?
Show me how you might solve the problem?
I am hoping that students will count up from 85 to 100 using coins or a number grid, or tens frame or number line. I am assuming from past work with students that they all know that a dollar is 100 pennies. If your students did not know that you might want to pick a different set of numbers that are closer to your students' understanding. Students record their thinking in their journals.