options: Statistics & Probability: students learn to analyze and produce data distributions, and build understanding of univariate and bivariate data. They learn to interpret data, make statistical inferences, justify conclusions, understand rules of probability, and use probability to make decisions.

Ratios & Proportional Relationships: students learn to recognize, describe, represent, and reason with ratios, rates, proportional relationships, and percent.

Number Systems and Quantity: students learn to understand the complex number system and reason quantitatively.

Operations & Algebra: students learn to solve problems using algebraic thinking and operations such as addition, subtraction, multiplication, and division. They may learn to identify and explain arithmetic patterns, evaluate or manipulate numerical expressions, and reason with equations and inequalities.

Functions: students learn to define, use, and evaluate functions to model relationships between quantities.

Geometry: students learn to classify geometric figures by their properties, and understand and compare the relationships between them. Students develop and use formulas to compute lengths, areas, and volumes, and they use transformations to generate new shapes and compare existing ones. Geometry can be studied with and without coordinates.

Number & Operations in Base Ten: students learn to work with the base-ten system and build place value understanding.

Modeling: students learn to choose and use appropriate mathematics and statistics to analyze real-world empirical situations, improve decisions, and report on their conclusions and the reasoning behind them.

Measurement & Data: students learn to work with data and measure attributes such as time, money, length, area, and volume. They may learn to compare measurements to operations and convert between different units of measure.

Counting & Cardinality: students learn to know number names and the count sequence, count to tell the number of objects, and compare numbers.

Number & Operations - Fractions: students learn to understand fractions as numbers and may work with them using addition, subtraction, multiplication, and division.
problem_activity: Narrative
The purpose of this activity is for students to consider possible mistakes when multiplying large numbers. Monitor for students who:
revise their answer after examining Kiran’s mistake.
recognize that
\(650 \times 10 = 6,\!500\)
so
\(650 \times 27\)
has to be much greater than 5,850.
can explain why Kiran should be multiplying
\(650 \times 2 \times 10\)
.
recognize that
\(20 \times 50 = 1,\!000\)
so there should be three zeros in the second partial product.
When students determine Kiran's error and make sense of his work, they interpret and critique the work of others (MP3).
MLR1 Stronger and Clearer Each Time.
Synthesis: Before the whole-class discussion, give students time to meet with 2–3 partners to share and get feedback on their response to “what parts of Kiran’s work do you agree and disagree with?” Invite listeners to ask questions, to press for details and to suggest mathematical language. Give students 2–3 minutes to revise their written explanation based on the feedback they receive.
Advances: Writing, Speaking, Listening
Launch
Display or write for all to see.
\(650 \times 27\)
Display each number in a different corner of the room:
14,000
18,000
13,000
19,000
“When I say go, stand in the corner with the number that you think is the most reasonable estimate for
\(650 \times 27\)
. Be prepared to explain your reasoning.”
1 minute: quiet think time
Ask a representative from each corner to explain their reasoning.
“Does anyone want to switch corners?”
Ask a student who switched corners to explain their reasoning.
“Now you are going to find this product and analyze some work.”
Activity
Groups of 2
5–7 minutes: partner work time
Student Facing
Find the value of the product.
[IMG]
Below is Kiran’s work finding the value of the product
\(650 \times 27\)
. Is his answer reasonable? Explain your reasoning.
[IMG]
What parts of the work do you agree with? Be prepared to explain your reasoning.
What parts of the work do you disagree with? Be prepared to explain your reasoning.
Look at your solution to problem 1. Is there anything you want to revise? Be prepared to explain.
Student Response
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for free access to Student Response.
Activity Synthesis
Ask previously identified students to share their thinking.
Display Kiran's work.
“Why doesn’t 5,850 make sense?” (
\(650 \times 10 = 6,\!500 \)
so
\(650 \times 27\)
should be a lot larger than 6,500.)
“What makes sense about Kiran’s work?” (
\(650 \times 2 =1,\!300\)
, but he needs to multiply
\(650\times2\times10\)
.)
Display a student's solution or the image from the student solution.
“How do we know that 17,550 is a reasonable value for the product?” (Because
\(600 \times 30 =18,\!000\)
.)


correct_option_index: 6