# Lesson 9

Resolvamos acertijos numéricos

### Lesson Purpose

The purpose of this lesson is for students to use their understanding of place value to solve number riddles.

### Lesson Narrative

In this lesson, students use their understanding of place value to determine a secret number and justify why the number matches the clues. When students solve the riddles, they have opportunities to look for and make use of the base-ten structure of numbers (MP7). In the synthesis, students discuss and solve a number riddle.

If students need additional support with the concepts in this lesson, refer back to Unit 4, Section B in the curriculum materials.

• Representation
• MLR8

### Learning Goals

Teacher Facing

• Apply place value understanding to solve number riddles.

### Student Facing

• Resolvamos acertijos numéricos.

### Required Materials

Materials to Gather

Materials to Copy

• Number Riddle Cards, Spanish

### Required Preparation

For the lesson synthesis, create a chart with clues. Leave a few lines in between each clue. Fold the chart paper so that only the first clue is showing.
• My number has more than 6 tens.
• My number is less than 100.
• My number has 8 tens.
• My number is the sum of $$51 + 32$$.

Activity 2:

• Create enough riddles from the Number Riddle Cards so each group of 2 students can have a different riddle. Fold the gray cards. Place each set of clues in a bag or envelope and label based on the letter of the riddle.

### Lesson Timeline

 Warm-up 10 min Activity 1 10 min Activity 2 25 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

As you finish up this unit, reflect on the norms and activities that have supported each student in learning math. List ways you have seen each student grow as a young mathematician throughout this work.