options: 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.

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

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.

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.

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.

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 & Operations - Fractions: students learn to understand fractions as numbers and may work with them using addition, subtraction, multiplication, and division.

Functions: students learn to define, use, and evaluate functions to model relationships between quantities.
problem_activity: Narrative
The purpose of this lesson is for students to learn stage 1 of the center, How Close? Students pick a given number of digit cards and then choose a subset of those to make an expression that yields a number as close as possible to 20.
Required Materials
Materials to Gather
Connecting cubes or two-color counters
Double 10-frames
Number cards 0–10
Materials to Copy
How Close? Stage 1 Recording Sheet
Launch
Groups of 2
Give each group a set of number cards, two recording sheets, and access to double 10-frames and connecting cubes or two-color counters.
“We are going to learn a game called How Close? Add to 20. Let's play the first round together.”
“First we take out any card that has the number 10. We will not use those cards for the game.”
Display 5 cards.
“I can choose two or three of these cards to add to get as close to 20 as I can. What cards should I choose?”
1 minute: quiet think time
2 minutes: partner discussion
Share responses.
“I write an equation with the numbers I chose and the sum of the numbers.”
Demonstrate writing the equation on the recording sheet.
“The person who gets a sum closer to 20 gets a point for the round. Then you each get more cards so you always have five cards to choose from. Play again. The person who gets more points wins.”
Activity
10 minutes: partner work time
Activity Synthesis
Invite students to share their methods for making a sum close to 20.


correct_option_index: 4