Lesson 13

This Number Talk encourages students to use what they know about place value and making a ten to find the value of sums mentally. The strategies elicited here will be helpful later in the lesson when students add two-digit numbers within 100. When students share how they look for ways to add by place and decompose addends to make a ten, they look for and make use of the base-ten structure of numbers and the properties of operations (MP7).

• 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 pueden formar una decena para encontrar el valor de \(67 + 14\)?” // “How can you make a ten to find the value of \(67 + 14\)?” (67 needs 3 more to make 10. That 3 can come from the 4 ones in 14.)

The purpose of this activity is for students to learn the first stage of a new center activity, Target Measurements. In this stage, students try to draw a line segment as close as possible to the length of the target measurement in whole inches or centimeters.

• Groups of 2
• Give each group a recording sheet and access to centimeter and inch rulers.
• “Vamos a aprender a jugar una nueva actividad del centro que se llama ‘Medidas objetivo’” // “We are going to learn how to play a new center activity called Target Measurements.”
• “En este centro, ustedes y su compañero dibujan un segmento de recta que se acerque tanto como sea posible a una longitud objetivo” // “In this center, you and your partner work together to draw a line that is as close as possible to a target length.”
• “Cuando sea su turno de dibujar, escojan una longitud en pulgadas o en centímetros. Si escogen pulgadas, no pueden escoger una longitud mayor que 10 pulgadas. Si escogen centímetros, no pueden escoger una longitud mayor que 30 centímetros” // “When it’s your turn to draw, choose a length in inches or centimeters. If you choose inches, you cannot choose a length longer than 10 inches. If you choose centimeters, you cannot choose a length longer than 30 centimeters.”
• Demonstrate choosing a length.
• “Si no es su turno de dibujar, su tarea es estar atentos a la línea que su compañero esté dibujando y decirle que pare cuando ustedes piensen que el segmento de recta tiene la misma longitud que la medida objetivo” // “If you are not drawing, your job is to watch the line and tell your partner to stop when you think the line they are drawing is the same length as the target measurement.”
• Select a student volunteer, or ask the class to be your partner. Demonstrate drawing a line segment using a straightedge.
• “Luego, ambos van a medir la longitud del segmento de recta y a encontrar la diferencia entre la longitud real y la longitud objetivo. El valor de la diferencia es el puntaje para el compañero que dijo ‘para’” // “Then both of you will measure the length of the line and find the difference between the actual length and the target length. The value of the difference is the score for the partner who said ‘stop.’”
• Demonstrate measuring the line and recording the target length, actual length, and difference in the place for Partner B on the recording sheet.
• “Tomen turnos para dibujar. Después de 8 rondas, sumen sus puntajes. El compañero con el menor puntaje es el ganador” // “Take turns drawing. After 8 rounds, add up your scores. The partner with the lowest score is the winner.”

• 10 minutes: partner work time
• Monitor for students who attempt longer lengths and come close to their target measurement.

• “¿Alguien dibujó un segmento de recta que tuviera la misma longitud que su longitud objetivo? Si no, ¿qué tan cerca estuvieron?” // “Did anyone draw a line segment that was the same length as your target length? If not, how close did you get?”
• “Cuando trabajaron con su compañero, ¿cuál fue su estrategia para dibujar segmentos de recta tan cercanos como fuera posible de su longitud objetivo?” // “What was your strategy when working with your partner to draw line segments that were as close as possible to your target length?”

The purpose of this activity is for students to learn stage 4 of the Number Puzzles center. Students use digit cards to make addition and subtraction equations true. They work with sums and differences within 100 with composing and decomposing.

After they participate in the center, students can choose to continue to play Number Puzzles or choose one of the estimation and measurement centers.

• Estimate and Measure
• Target Measurements

Gather materials from:

• Number Puzzles, Stages 4
• Estimate and Measure, Stage 2
• Target Measurements, Stage 1

• Groups of 2
• Give each group a set of digit cards and a gameboard.
• “Ahora vamos a aprender una nueva forma de jugar el centro ‘Acertijos numéricos’” // “Now we are going to learn a new way to play the Number Puzzles center.”
• “En esta etapa, ustedes usan sus tarjetas de dígitos para hacer que cada ecuación sea verdadera. Es posible que tengan que pensar en componer o en descomponer una decena” // “In this stage, you use your digit cards to make each equation true. You may need to think about composing or decomposing a ten.”

• 10 minutes: partner work time
• “Ahora pueden escoger otro centro. También pueden seguir jugando ‘Acertijos numéricos’” // “Now you can choose another center. You can also continue playing Number Puzzles.”
• 10 minutes: center work time

• “¿Qué les gustó de las actividades en las que trabajaron hoy?” // “What did you like about the activities you worked on today?”