In this activity, students revisit two algorithms for multiplying numbers. They recall that in the standard algorithm, the digit in one factor is multiplied by each digit in the other factor, but the partial products are not recorded on separate lines. Rather, the standard algorithm condenses multiple partial products into a single product. 

• Select students to share their responses to the second set of questions.
• If not mentioned in students’ explanations, highlight that:
  • The result of is 15, a two-digit number, so 10 of the 15 ones are composed as 1 ten above the tens place and added to the 3 tens that result from .
  • 1 ten and 3 tens make 4 tens.
• Poll the class on whether their preferred method is A, B, or dependent on the problem. Select a student from each camp to explain their reason.

Earlier, students compared and made connections between two algorithms for multiplying a multi-digit number and a single-digit number. In this activity, students compare an algorithm that uses partial products with the standard algorithm for multiplying 2 two-digit numbers. As students analyze and critique each method, they practice looking for and making use of the base-ten structure of whole numbers (MP7). 

• Invite students to share how they used each method to show that ​ ​ and ​ ​.