Have students work in small groups of 3 or 4 to answer Questions 7–9. These questions contain number riddles that give clues using the words multiple, factor, prime number, and square number.
Refer to Expectation 1 on the Math Practices page in the Reference section of the Student Guide to help students understand the riddle for Question 7.
- What does the riddle tell you? Are there any words you need to understand to be able to solve the riddle? (prime number and square number)
- Where can you go to find what the words mean? (We can look back in our Student Guide to where we studied those words.)
- What do you need to find out? (Possible response: What the prime numbers are between 10 and 20. Then, find which one is one more than a square number.)
Ask each small group to assign a recorder to write down how the group solved the riddle for each question. Review Math Practices Expectation 5 to help students organize their explanations for how they solved the riddle.
After students have been working on Question 7 for several minutes, ask:
- What kinds of things should you show in your explanation so someone can understand how you solved the riddle? (Possible responses include listing each step, writing down the possible numbers for each clue, circling possible numbers, crossing out numbers that don't work, and telling why numbers are crossed off.)
Ask for volunteers to show their work and explain their solution paths. You can ask a different group to show their work for each of the three problems. Ask the class to critique the explanations based on Math Practices Expectation 5.
- Did they show how they arrived at their solution?
Are any steps missing?
- Would someone who has never seen these riddles before be able to understand what they did from their explanation?
- Can you understand their thinking?
- Do you know what each of the numbers in the explanation means? Did they use prime number and square number in the explanation?
- Do you know why numbers are listed, circled, or crossed out?
- Is it clear what number is the final answer to the riddle?
- What questions do you want to ask, so that you understand the solution better?
- What needs to be added, so that the explanation is clearer?
Ask students to revise their written explanations based on Math Practices Expectation 5 and what they learned from the discussion.
