Lesson 12

The purpose of this True or False is for students to demonstrate strategies and understandings they have for adding decimals. These understandings help students deepen their understanding of the properties of operations and will be helpful later in the lesson when students will need to be able to add decimals.

• Display one equation.
• “Hagan una señal cuando sepan si la ecuación es verdadera o no, y puedan explicar cómo lo saben” // “Give me a signal when you know whether the equation is true and can explain how you know.”
• 1 minute: quiet think time

• Share and record answers and strategy.
• Repeat with each equation.

• Display the first and third equations.
• “¿Cómo pueden justificar su respuesta sin evaluar cada lado?” // “How can you justify your answer without evaluating both sides?” (For the first problem, I noticed that there are 9 tenths on the right and left and also 10 hundredths. For the third problem, I saw that the right hand side is almost 2 so it's much larger than the left hand side.)

The purpose of this activity is for students to practice adding decimals. There are two versions of the game, Race to One and Race to One Tenth. Students can choose which version to play, or, if there is time, play both versions of the game. Consider playing a round of the game with students during the launch to demonstrate how it is played.

• Each group of 2 needs a number cube.

• Groups of 2
• “Tómense un minuto para leer las instrucciones del juego ‘Carrera hasta uno’ o ‘Carrera hasta una décima’” // “Take a minute to read over the directions for Race to One or Race to One Tenth.”
• 1 minute: quiet think time
• “Antes de que empecemos, ¿tienen alguna pregunta?” // “Are there any questions before we get started?”
• Give students a set of cards.

• “Jueguen ‘Carrera hasta uno’ o ‘Carrera hasta una décima’” // “Play Race to One or One Tenth.”
• 10–12 minutes: partner work time

• “¿En qué se parecen los juegos ‘Carrera hasta uno’ y ‘Carrera hasta una décima’?” // “How are the two games, Race to One and Race to One Tenth the same?” (In both cases, I ended up close to the goal value and then had to keep rolling, hoping I got the right number.)
• “¿En qué son diferentes los juegos?” // “How are the games different?” (In Race to One, I am aiming for 1 and in Race to One Tenth I am trying to get 0.1. When I get close to 1 in Race to One I have to choose hundredths and when I get close to 0.1 in Race to One Tenth I have to choose thousandths.)
• “En el juego ‘Carrera hasta uno’, ¿cómo decidían si querían que el número que sacaban representara décimas o centésimas?” // “How did you decide whether to have a number represent tenths or hundredths in Race to One?” (If I wasn’t close to one, I would have it represent the larger value.)

• Each group of 2 needs a paper clip.

• Groups of 2
• “Tómense un minuto para leer las instrucciones de ‘Carrera de números decimales hasta 500’​​​​” // “Take a minute to read over the directions for Decimal Race to 500.”
• 1 minute: quiet think time
• Give students paper clips.

• “Jueguen ‘Carrera de números decimales hasta 500’ con su compañero” // “Play Decimal Race to 500 with your partner.”
• 10–15 minutes: partner work time

• “¿Qué número escogerían formar si al girar la ruleta les salieran 1, 8 y 4? ¿Por qué?” // “What number would you choose to make if you spun 1, 8, and 4? Why?” (84.1 because that’s the biggest number I can make with those digits.)
• “¿Se puede ganar el juego en una ronda? ¿Cómo?” // “Is it possible to win the game in one turn? How?” (Yes, I can spin 6, 2, and 8 and then can make 862 and that’s the end of the game.)
• “Si quisieran ganar el juego rápidamente, ¿cuáles serían los peores números que les podrían salir?” // “What numbers are the worst numbers to spin if you want to win the game quickly?” (Odd numbers because they only count for tenths, hundredths, or thousandths. Also 0 is no good unless there are some other even numbers.)
• “¿Pueden pensar en una forma de cambiar este juego para volverlo más retador?” // “Can you think of a way to change this game to make it more challenging?” (Make it so you have to land exactly on 500.)