Lesson 12 Equations with Unknowns
Let’s represent equations with a ? for the unknown.
Warm-up True or False: Making Tens
Decide if each statement is true or false. Be prepared to explain your reasoning.
Activity 1 Number Line Riddles
Solve riddles to find the mystery number.
For each riddle:
Write an equation that represents the riddle and write a ? for the unknown.
Write the mystery number. Represent the equation on the number line.
I started at 15 and jumped 17 to the right. Where did I end?
Equation:
Mystery number:
I started at a number and jumped 20 to the left. I ended at 33. Where did I start?
Equation:
Mystery number:
I started on 42 and ended at 80. How far did I jump?
Equation:
Mystery number:
I started at 76 and jumped 27 to the left. Where did I end?
Equation:
Mystery number:
I started at a number and jumped 19 to the right. I ended at 67. Where did I start?
Equation:
Mystery number:
I started at 92 and ended at 33. How far did I jump?
Equation:
Mystery number:
Activity 2 Make the Equations True
Find the number that makes each equation true.
Show your thinking on the number line.
Practice Problem
Problem 1
I started at a number on the number line and jumped back 37. I landed at 26. Where did I start?
Write an equation with a ? for the unknown.
Find the number that makes the equation true.
Represent your thinking on the number line.