This activity introduces students to the standard algorithm for multiplication. Students make sense of it by comparing and contrasting it to an algorithm that uses partial products for multiplying three- and four-digit numbers by one-digit numbers where no regrouping is necessary. When they interpret the given student work showing the standard algorithm students construct a viable argument for what Kiran did in his calculation (MP3). They also have an opportunity to make use of the structure they notice to compute the value of other products.

• Select students to share and explain their calculations of the last two products.
• Consider demonstrating the process of Kiran’s strategy to find .
• “La estrategia de Kiran se llama el ‘algoritmo estándar de multiplicación’. En la siguiente actividad, vamos a estudiar más a fondo este algoritmo” // “Kiran’s strategy is called the ‘standard algorithm for multiplication.’ We’ll take a closer look at this algorithm in the next activity.” 

The purpose of this activity is for students to compare the standard algorithm for multiplication and an algorithm that uses partial products. The focus of the Lesson Synthesis is on the convention used for composing a new unit and how it connects to their work with the standard algorithm for addition.

• “En la síntesis de la lección, vamos a comparar las formas en las que llevamos un registro de los productos parciales” // “In the Lesson Synthesis, let’s compare ways we kept track of the partial products.”