Lesson 10 Using Algorithms with Partial Products: 2 Two-digit Numbers

    • Let’s try to multiply two-digit numbers with an algorithm that uses partial products.

Warm-up Number Talk: Products

Find the value of each expression mentally.

Activity 1 Partial Products, Recorded

Tyler used an algorithm to find the value of .

multiply. sixty 4 times eighty 7.
  1. How do you think he arrived at the last five numbers? Record your thinking. Be prepared to share it with a partner.

  2. Use Tyler’s method to find the value of . Then, draw a diagram to check your answer.

Activity 2 Han’s Multiplication Mishap

Problem 1

Decide with your partner who will find each product. Show your reasoning.

  1. multiply. 19 times 32 equals.
  2. multiply. 32 times 19 equals.

Problem 2

Here is Han’s computation of .

multiply. fifty 1 times 47. 7 rows.
  1. What error or errors did Han make?

  2. Show the correct computation for finding the value of .

    multiply. fifty 1 times 47 equals.

Practice Problem

Problem 1

Here is an incomplete calculation that uses partial products of .

  1. Write multiplication expressions that the numbers 15, 180, 200, and 2,400 each represent. Then, find the value of .

    multiply. sixty 5 times 43.
  2. Find the value of the product .