standard_description: Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.
problem_activity: Narrative
The purpose of this True or False is for students to demonstrate strategies and understandings they have for adding decimals. These understandings help students deepen their understanding of the properties of operations and will be helpful later in the lesson when students will need to be able to add decimals.
Launch
Display one equation.
“Give me a signal when you know whether the equation is true and can explain how you know.”
1 minute: quiet think time
Activity
Share and record answers and strategy.
Repeat with each equation.
Student Facing
Decide if each statement true or false. Be prepared to explain your reasoning.
\(0.99 + 0.1 = 0.9 + 0.1 + 0.09\)
\(0.99 + 0.01 = 0.9 + 0.1\)
\(0.99 + 0.1 = 1.99\)
Student Response
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Activity Synthesis
Display the first and third equations.
“How can you justify your answer without evaluating both sides?” (For the first problem, I noticed that there are 9 tenths on the right and left and also 10 hundredths. For the third problem, I saw that the right hand side is almost 2 so it's much larger than the left hand side.)


aligns: no