Lesson 10

• Display one statement.
• “Give me a signal when you know whether the statement is true and can explain how you know.”
• 1 minute: quiet think time

• Share and record answers and strategies.
• Repeat with each equation.

• “How can you explain your answer without finding the value of the sums on the right side?”

The purpose of this activity is for students to write number riddles. Students choose a secret number between 1 and 120, and write four clues that will help their classmates identify the number. As students work, the teacher should review students’ riddles and monitor for groups that may need help writing clues.

• Groups of 2
• Give each group four index cards, a bag or envelope, and access to connecting cubes in towers of 10 and singles.
• “When we solved number riddles, what types of clues did we see?” (number of tens, number of ones, more than, less than, addition)
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Record responses.

• “Now you will write a number riddle with your partner. You will write four clues. One clue should be an addition expression that will be the last clue. Write each clue on an index card and make sure that your number fits all the clues. Fold the card with the addition expression in half.”
• 10 minutes: partner work time
• Consider asking:
  • “What is your secret number?”
  • “What number(s) is your secret number greater than? Less than?”
  • “What do you know about the tens and ones in your secret number?”
  • “What numbers can you add (subtract) to get this number?”

If students write fewer than three clues, consider asking:

• “What do you know about your secret number?”
• “How can you write a clue using ‘greater than’ or ‘less than’ or __ tens or ones?”

• “Put your clues in an envelope and write your names on the envelope.”

The purpose of this activity is for students to apply place value reasoning to solve number riddles written by their classmates. When students solve the number riddles they use their understanding of the number sequence and place value (MP7).

• Each group of 2 needs to begin with a riddle envelope from the previous activity. 

• Groups of 2
• Give each group a riddle envelope and access to connecting cubes in towers of 10 and singles.

• “Now you are going to solve your classmates’ riddles. Use your workbook page as a place to record your ideas as you solve. When you finish solving a riddle, put it back in the envelope and look for another group who is ready to trade riddles with you.”
• 15 minutes: partner work time

• “Were there any number riddles that were challenging to solve? Why were they more challenging than the other riddles?”