options: Use place value understanding and properties of operations to perform multi-digit arithmetic. (A range of algorithms may be used.)

Work with numbers 11–19 to gain foundations for place value.

Use place value understanding and properties of operations to add and subtract.

Generalize place value understanding for multi-digit whole numbers.
Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000.

Use place value understanding and properties of operations to perform multi-digit arithmetic.
Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000.

Perform operations with multi-digit whole numbers and with decimals to hundredths.

Extend the counting sequence.

Understand the place value system.

Understand place value.
problem_activity: Narrative
The purpose of this warm-up is to draw students’ attention to the first few multiples of 45, which will be helpful as students continue to work with benchmark angles and use a protractor to measure angles. Students have the skills to perform the multiplication in each equation, but computing each product may be time-consuming. Students can more efficiently tell if the equations are true or false if they consider properties of operations and look for and make use of structure.
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 statement.
Student Facing
Decide if each statement is true or false. Be prepared to explain your reasoning.
\(2 \times 45 = 6 \times 15\)
\(4 \times 45 = 2 \times 90\)
\(3 \times 45 = 180 - 90\)
\(6 \times 45 = 45 + 90 + 135\)
Student Response
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Activity Synthesis
Some students may notice that it is handy to think in terms of
\(2 \times 45\)
because it would mean dealing with multiples of 90 rather than multiples of 45. Highlight their explanations.
If no students decomposed expressions such as
\(3 \times 45\)
,
\(4 \times 45\)
, and
\(6 \times 45\)
into sums of
\(1 \times 45\)
and
\(2 \times 45\)
, discuss how this could be done. (See sample responses.)


correct_option_index: 4