Students will be able to sort objects into groups of ten and add multiples of ten to find the total number of objects.
- Seat children in a circle on the rug.
- Show students a large bag of counting objects, such as paper clips.
- Have children estimate the total number of paper clips. Explain that to estimate means to carefully guess the number of paper clips based on what they see. Record their estimations on the board.
- Discuss with students how they made their estimates.
- Explain that the class could count the paper clips one by one to determine the total number. Today they will learn a faster way to calculate the total number by sorting the paper clips in groups of 10 and then adding.
Explicit Instruction/Teacher modeling(15 minutes)
- Show students another example of approximately 100 counting objects, such as pennies.
- Model estimating the total number of pennies. Show students how to divide up the pennies into groups of 10, and then model counting by tens to calcuate the total number of pennies. Reflect on the accuracy of your estimation.
- Return to the paper clip collection from the introduction. Tell students that they will work together as a class to calculate the total number of paper clips and check the accuracy of their estimation. Divide the paper clips among small groups of four students.
- Have students work to sort their items into groups of 10. Students can create strings of 10 linking paper clips or connecting links, or place groups of 10 beads or beans into small cups.
- When students have finished grouping the items, bring the class back together to collect any leftover items. Group these items as well.
- Ask students to turn and talk to a partner about how creating groups of 10 with the paper clips will help them figure out the total number.
Guided Practice(10 minutes)
- Display a hundreds chart and remind students that they could count each paper clip individually to calculate the total number.
- Count chorally from 1–10 with the class, pointing to each number on the hundreds chart.
- Have one group bring their paper clips linked and sorted into strings of ten to the front.
- Say, "I see there are 10 paper clips in this string." Write the number 10 on the board.
- Ask students, "As I count more paper clips, what am I doing?" Students should respond that you are adding paper clips.
- Remind students that since you are adding more to the total, you will use the plus sign as you write a plus sign next to the 10.
- Ask students how many paper clips are in the second string. Write the equation 10 + 10 = 20, and show students that 10 is below 20 on the hundreds chart.
- Continue to record the total number of clips plus 10 until you finish counting all the paper clips. Any left over paper clips were not grouped as a 10 should be added as ones.
- Chorally count by tens as a class as you point to the sum of each equation.
Independent working time(10 minutes)
- Have students work with a partner. Have them walk around the room, pointing to each group of 10 as they recount the paper clips.
- Bring students back to the rug. Have individual students call out the multiple of 10 as you choose volunteers to return a group of paper clips to the original container.
- Give students a copy of the hundreds chart as they work with a partner to recount the total number of paper clips.
- Limit students to counting 100 paper clips.
- Intruct students to write equations that demonstrate their understanding of adding multiples of 10.
- Allow students to count a larger number of objects.
- Observe that students count accurately as they practice recounting the paper clips with a partner. Then, have students call out multiples of ten as they return all the paper clips to you.
- Tell students to turn and talk with a partner about how grouping large numbers of objects by 10 can help them to count.
- Choose a few students to share out ideas with the whole class.
Review and closing(5 minutes)
- Return to the original estimate of the total number of paper clips.
- Tell students to turn and talk to a partner about how close their estimate was to the actual amount. Was the actual amount more, less, or about the same as their estimate?
- Remind students that grouping large numbers of items and then counting by tens can help them count more quickly and accurately.