Lesson 4

This Number Talk encourages students to think about how to use the addition and subtraction facts they know and their understanding of place value to mentally find values of expressions. The strategies elicited here will be helpful as students use the facts they know to develop fluency with addition and subtraction within 100.

Students may notice that calculating \(6 - 3\) is repeated in each expression and use this to mentally find the values (MP8). Students must also attend to precision in how they describe how they use known facts or other methods (MP6), especially when they describe subtracting by place. Encourage students to tell more about their strategy if they use unclear language to describe their method and to reflect on how their description could be interpreted differently without more precise language. For example, if students say they knew \(66-30=36\) because they know \(6-3\), ask students to explain how that fact helped them subtract.

• Display one expression.
• “Hagan una señal cuando tengan una respuesta y puedan explicar cómo la obtuvieron” // “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

• Record answers and strategy.
• Keep expressions and work displayed.
• Repeat with each expression.

• “¿En qué se parece cada expresión a \(6 - 3\)? ¿En qué son diferentes las expresiones?” // “How is each expression like \(6 - 3\)? How are the expressions different?” (Each expression has the digits 6 and 3. In each expression you could use what you know about \(6 - 3\). Some expressions you are finding 6 ones \(-\) 3 ones. In some expressions you are finding 6 tens \(-\) 3 tens.)

The purpose of this activity is for students to learn stage 3 of the Capture Squares center. Capture Squares was introduced in grade 1. In this stage, students spin to get a number (6–10) and flip a card (0–10) and find the value of the sum. The spinner includes a wild space where students can choose their own number. They find the value of the sum on the game board and connect 2 dots that are adjacent to the number. If that line closes the square, they capture it and shade it in their color. The player to shade in 3 squares first is the winner. 

• Groups of 2
• Give each pair of students a copy of the game board, the spinner and a paper clip, a set of cards, and access to crayons or colored pencils.
• “Vamos a jugar un juego” // “We are going to play a game.”
• Spin the spinner and draw a card.
• “¿Cómo podría encontrar el valor de la suma de estos dos números?” // “How could I find the value of the sum of these two numbers?”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.
• Use a suggested method or select a volunteer to show how to find the value.
• “Ahora, encuentro el cuadrado que tiene el valor de mi suma. Dibujo una línea que conecte dos puntos de ese cuadrado” // “Now, I find the square that has the value of my sum. I draw a line connecting two dots on that square.”
• “Si la ruleta cae en el comodín, pueden escoger cualquier número para que sea uno de sus sumandos” // “If the spinner lands on the wild space, you can pick any number to be one of your addends.”
• Repeat 1–2 more times, as needed.
• “Cuando dibujo la línea que completa un cuadrado, coloreo ese cuadrado con mi color. Gana el jugador que primero coloree 3 cuadrados.” // “If I draw the line that completes the square, I shade in that square with my color. The first player to shade in 3 squares is the winner.”

• 12 minutes: partner work time 
• Monitor for a variety of student strategies to share in the synthesis.

• Invite selected students to share their strategies. 
• “Cuando la ruleta cayó en el comodín, ¿cómo decidieron qué número escoger?” // “When the spinner landed on the wild spot, how did you decide what number to pick?”

The purpose of this activity is for students to learn stage 6 of the Five in a Row center. Five in a Row was introduced in grade 1. In this stage, students add within 100 including sums that require composing a ten when adding by place. Partner A chooses two numbers and places a paper clip on each number. They add the numbers and place a counter on the sum. Partner B moves one of the paper clips to a different number, adds the numbers, and places a counter on the sum. Students take turns moving one paper clip, finding the value of the sum, and covering it with a counter. The winner is the first one to get five counters in a row.

• Groups of 2
• Give each group a gameboard, 2 paper clips, and two-color counters.
• “Vamos a aprender un juego que se llama ‘Cinco en línea’. Juguemos una ronda juntos” // "We are going to learn a game called Five in a Row. Let’s play a round together."
• Display the game board.
• “Primero voy a escoger dos números de las filas grises para sumarlos. Pongo un clip en un número de la fila de arriba y otro en un número de la fila de abajo. Después los sumo” // “First I need to pick two numbers to add from the grey rows. I put a paper clip on one number in the top row and one number in the bottom row. Then I add them together.”
• Pick two numbers and add them.
• “El valor de mi suma es ____. Ahora busco el número en el tablero de juego y lo cubro con una ficha. Ahora es el turno de mi pareja” // “The value of my sum is _____. Now I look for the number on the gameboard and cover it with a counter. Then it is my partner’s turn.”
• “Mi pareja solo puede mover uno de los clips. Después debe encontrar la suma de los dos números” // “My partner can only move one of the paper clips. Then they must find the sum of the two numbers.”
• If needed, select a student volunteer to be Partner B to show the steps.
• “Antes de que empiecen, deben decidir con su pareja quién va a usar el lado rojo de las fichas y quién va a usar el lado amarillo. Después, por turnos, muevan un clip y sumen los números. Gana la primera persona que tenga cinco fichas en línea en el tablero. Las fichas pueden estar en una línea de un lado a otro, de arriba a abajo o en diagonal” // “Before you begin, you and your partner need to decide who will use the red side of the counters, and who will use the yellow side. Then take turns moving one paper clip and adding the numbers. The first person to get five counters in a row on the game board wins. The counters can be in a row across, up and down, or diagonal.”

• 12 minutes: partner work time

• Display a game board with the center column covered with red counters except for the 33 at the bottom. 
• Show that one paper clip is on 8. 
• “Este es mi tablero de juego. ¿En dónde pondrían el otro clip?” //“This is my game board. Where would you put the other paper clip? (I would put it on 25 since \(25 + 8 = 33\) and then you could cover the last number in the column and have five in a row.)