Race to 100

Explicit Instruction/Teacher modeling

• Tell students that today they will learn about place value, which is the value of a digit depending on its place in a number. Because the digits one and two are in different positions in the numbers 12 and 21, these numbers are different, so Sara's little sister is incorrect.
• Have students count with you as you sketch the values of 12 and 21. Draw ten circles under the one in the tens place of 12, and two circles under the two in the ones place. Repeat with the number 21. Have students repeat after you: "Ten and two, 12. Twenty and one, 21."
• Define digit as a single number. Have students share with a partner an example of a place where they have seen one-digit numbers, such as the back of a football jersey or on a number magnet. Create a chart divided into three colums, and list examples of one-digit numbers in the far left column.
• List examples of two-digit numbers in the middle column, and three-digit numbers in the far right column.
• Ask students to define "place." Place, or position, is where something is. Return to the example of 12 and 21. Show students that the one is on the left in 12, the one is on the right in 21. Ask students if they would rather have 12 dollars or 21 dollars. Although the digits are the same, the value of the numbers is different because of where the digits are in the number.
• Discuss the meaning of "value." Review that value means how much something is worth. In the number 14, the one is worth 10.
• Tell students that today they will play a game where they will race with a partner to collect 100 cubes. Display a cube for reference. Once students have 10 single cubes, they will group the cubes as a 10. To group means to put things that are the same together.
• Explain that when we tell students to "get in their groups," we mean work with others who are in the same bunch. To play the game, students will put cubes in groups of 10.

Guided Practice

• Display the Place Value Mat: Two-Digit Numbers worksheet on a document camera or tape it to the board.
• Distribute the worksheet and approximately 30 cubes to each student.
• Tell the students you will play a few rounds together before excusing them to play with their partners.
• Create a chart titled "Race to 100" and list the rules:
  1. Roll the die.
  2. Add that many cubes to the "ones" side.
  3. Group 10 ones as a 10 and move the tower to the "tens" side.
• The partner who rolls should say, "I have ____ tens and ____ ones. I have ____ cubes."
• Roll the die, and add cubes to the “ones” side of the game board. Model, "I have zero tens and six ones. I have six cubes." Students mirror on their game boards, and repeat the sentence chorally.
• Once you have more than 10 total cubes, group a 10. For example, if you have nine cubes, and then roll a three, first add three cubes to the “ones” side. Tell students, "I have more than 10 cubes in the ones place. I need to group 10 ones as a 10." Model creating a tower of 10 cubes, and moving it to the "tens" side.
• Ask students what they think you should do with the remaining cubes. Since you do not have enough to compose a second 10, leave two cubes on the “ones” side.
• Model, "I have one 10 and two ones. I have 12." Students mirror on their game boards, and repeat.
• Continue to play as a class, rolling the dice, counting the cubes, regrouping as needed, and saying the number as tens and ones and as the numeral. Play until you have three groups of 10, or until students understand how to play the game.

Group work time

• Explain that students will now play Race to 100 with their partner. Refer to the instructions, and tell students to explain in their own words the directions to play the game with their partner.
• Pass out a die and more cubes to each partnership. Tell students that they will need to keep adding tens to the left of the Place Value Mat as they play.
• Remind students to work together to make sure that each partner is counting and composing tens correctly. Listen to hear that students say the total number as both tens and ones and the numeral.
• Students should take turns rolling the die and adding the correct number of cubes.
• When a student has 10 tens, or 100, they win! Students can clear the game board and play again.