In this activity, students check their progress toward fluent multiplication within 100. They do this by revisiting an activity from a previous unit, in which they sort multiplication expressions, from to , into groups: those that they know right away, those they can find quickly, or those they don’t know yet. Here, students sort the same set of expressions, share strategies for finding products they don’t know yet, and then practice finding five products of their choice.

• “What were some useful strategies for finding products you didn’t know yet?” (Using a product I already know to find the one I didn’t know yet. Using products of 2, 5, and 10 to figure out other products.)

The purpose of this activity is for students to learn Stage 3 of the Compare center to practice multiplying within 100. Students may compare expressions by finding the value of each or by reasoning about the features of the expressions (MP7). (For example, when comparing and , they see that both involve 12 groups, but in there are 2 more in each group than in .)

When students multiply 2 one-digit numbers, they should know these products from memory. When students multiply a one-digit number and a two-digit number, they should have an efficient method for finding the product, but do not need to know the product from memory. If students need more practice with their one-digit multiplication facts, consider having them use the cards from the first activity.

• “What were some useful strategies for comparing the expressions on the cards?” (Comparing by thinking about what the expressions mean, instead of by multiplying. For example, was greater than because it's 1 more group of 6. Breaking apart some of the large factors into smaller factors to make multiplying easier.)