Lesson 4

The purpose of this Number Talk is to elicit strategies and understandings students have for multiplying within 100 with one factor larger than 10. These understandings help students develop fluency and will be helpful when students find factor pairs of numbers later in the lesson.

In this activity, students have an opportunity to look for and make use of structure (MP7) as they use a combination of products of smaller factors to find products of larger factors.

• 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.

• “¿Cómo nos ayuda conocer el valor de las primeras dos expresiones a encontrar el valor de la tercera expresión?” // “How can knowing the value of the first two expressions help you find the value of the third expression?” (I can multiply in parts and add the smaller parts together to find a larger product.)

The purpose of this activity is for students to self-assess their own fluency with multiplication facts and practice the ones that are less familiar. Students are given a set of expressions. They sort them into categories of “know it right away,” “can find it quickly,” or “don’t know it yet.” Then, they identify products they don’t know (or don’t know well) yet, discuss strategies for finding those products, and practice using those strategies.

• Create a set of multiplication fluency cards from the blackline master for each group of 2.

• Groups of 1–2
• Give each group a set of fluency cards.
• “Tómense un momento para clasificar cada tarjeta en uno de los tres grupos” // “Take some time to sort the cards into one of the three groups.”
• 3–5 minutes: partner work time

• “Compartamos y practiquemos estrategias para encontrar productos que todavía no sabemos” // “Let’s share strategies for finding products we don’t know yet and practice with them.”
• “Escojan 5 hechos de multiplicación que todavía no sepan y escriban las expresiones. Van a practicar cómo encontrar estos productos” // “Choose 5 multiplication facts that you don’t know yet and record the expressions. These are the products you will practice finding.”
• 1 minute: independent work time
• “Ahora compartan su lista con su compañero. Discutan algunas estrategias que les ayudarían a encontrar los productos rápidamente. Después, tómense un momento para practicar cómo encontrar los productos que escogieron” // “Now, share your list with your partner. Discuss some strategies you could use to find the products quickly. Afterwards, take some time to practice finding the products you chose.”
• 3–5 minutes partner work time

To support students in making connections between multiplication facts they know and those they are still working on, consider asking: “¿Qué observas sobre los números en los hechos de multiplicación en los que todavía estás trabajando?” // “What do you notice about the numbers in the multiplication facts you are still working on?” or “¿Puedes pensar en un hecho de multiplicación relacionado que te ayude?” // “Can you think of a related multiplication fact that might be helpful?”

• “¿Cuáles son algunas estrategias útiles para encontrar productos que no conocen todavía?” // “What are some useful strategies for finding products you didn’t know yet?” (Think of a product I already know and use it to find the one I didn’t know yet. Imagine equal-size groups. Break the expressions into smaller numbers, find those products, and then add them.)

The purpose of this activity is for students to apply multiplication fluency within 100 to find factors of multiples within the range of 1–36. This game is Stage 1 of the center Find the Number. In this stage, students find all the factors for a given number.

One player chooses a number on the game board (1–36) and gets that many points. The second player covers all the factors of that number. The score of the second player is the sum of all of the covered factors.

Players take turns choosing the starting number. A player who chooses a number without any uncovered factors loses their next turn. When there are no numbers remaining with uncovered factors, the player with the most points wins.

• Groups of 2
• Give each group a copy of the blackline master and centimeter cubes.
• “Vamos a jugar un juego que se llama ‘Encuentra el número‘. Tómense unos minutos para leer las instrucciones” // “We are going to play a game called Find the Number. Take a few minutes to read the directions.”
• 2 minutes: independent work time
• “¿Qué preguntas tienen sobre el juego?” // “What questions do you have about the game?”
• Consider playing a demonstration round or asking questions such as:
  • “Si yo cubriera el número 9, ¿qué factores deberían cubrir ustedes?” // “If I covered the number 9, which factors would you cover?” (1, 3)
  • “¿Cuál sería su puntaje?” // “What would your score be?” (4)
  • “¿Cuál sería mi puntaje?” // “What would my score be?” (9)

• 10–15 minutes: partner game time

• “¿Qué estrategias les ayudaron en el juego?” // What strategies were helpful for the game?” (Choose numbers with fewer factors to keep your opponent’s score low.)