The purpose of this activity is to emphasize the importance of identifying the length of a unit when measuring (MP6). Students work in groups to measure the same length of string using straws. Students find and report measurements of different lengths because they are provided with straws of different lengths. In the Synthesis, students discuss that although the same length of string was measured, the measurements are different, because different length units were used. This sets students up to discuss what happens when everyone uses the same length unit in the next activity.

Straws may be replaced by pipe-cleaners or other rigid objects that can be cut to the specified lengths.

This activity uses MLR8 Discussion Supports. Advances: Listening, Representing

• “¿Cuál es la longitud de la cuerda de Priya?” // “How long is Priya’s string?”
• Record responses.
• “¿Por qué son diferentes nuestras medidas de la longitud?” // “Why are our length measurements different?” (Some groups maybe didn’t line up their straws correctly. Maybe the straws weren’t the same size.)
• 30 seconds: quiet think time
• 1 minutes: partner discussion
• Share responses.
• Invite previously identified students to demonstrate their measurements.
• “Ambos grupos empezaron desde el comienzo de la cuerda y alinearon pajillas sin dejar espacios ni superposiciones hasta llegar al final” // “Both of these groups started at the beginning of the string and lined up straws with no gaps or overlaps until they reached the end.”
• “¿Por qué las medidas son diferentes?” // “Why are the measurements different?” (The straws are different sizes. One group used short straws and one group used long straws.)
• “Las medidas son diferentes porque cada grupo usó diferentes unidades de longitud” // “The measurements are different because each group used different length units.”
• “Una unidad de longitud es la longitud del objeto que se usa para medir” // “A length unit is the length of the object you use to measure.”

The purpose of this activity is for students to understand why it is important to be precise about the length of the unit used to measure (MP6). All student groups use centimeter cubes to measure. After measuring, students compare their measurements with other groups. In the Synthesis, students discuss why each group's measurement is the same, or nearly the same, after they measured the length with cubes. Students are introduced to standard units, but do not need to use this term.

Representation: Internalize Comprehension. Invite students to identify which details were important to solve the problem in the first activity. Display the sentence frame, “La próxima vez que queramos medir la longitud de un objeto, voy a fijarme en que la herramienta para medir esté alineada con el objeto desde su extremo. Debo asegurarme de que no haya espacio entre las unidades que uso para medir” // “The next time we want to measure the length of an object, I will pay attention to how I line up the measuring tool with the end of the object to be measured, and make sure there is no space between the measuring units.”
Supports accessibility for: Organization, Attention

• Share and record measurements.
• “¿Por qué las medidas de longitud de todos los grupos son la misma o aproximadamente la misma?” // “Why is every group's measurements the same, or closer to the same, length?” (They are the same because we all used the same length unit. We all used cubes that have the same length.)
• As needed, restate student responses when they say the cubes are “the same” to emphasize that the cubes have the same length.
• Display a centimeter cube and a connecting cube.
• “Si algunos grupos hubieran usado estos cubos y otros grupos hubieran usado cubos encajables, ¿habrían sido iguales nuestras medidas? ¿Por qué?” // “If some groups used these cubes and other groups used connecting cubes, would our measurements have been the same? Why?” (It would not be the same because the cubes are not the same length.)
• “Usar pajillas y cubos como unidades de longitud puede ser confuso porque hay pajillas y cubos de muchos tamaños diferentes” // “Straws and cubes can be confusing to use as length-units because they can be lots of different sizes.”
• “Hay unidades que las personas en todo el mundo usan para medir porque siempre tienen el mismo tamaño. Estas unidades se llaman ‘unidades estándar’” // “There are units that people around the world use to measure that always have the same size. They are called standard units.”