standard_description: Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.
problem_activity: Narrative
The purpose of this activity is for students to learn stage 3 of the How Close center which was introduced in grade 1. In this stage, each student picks 7 cards and chooses 4 of them to create 2 two-digit numbers. Each student adds the numbers and the student whose sum is closest to 100 wins a point for the round. It is recommended that at this point in the year, students begin with a target number of 50 instead of 100 in this stage.
If students are not yet able to make 2 numbers that get close to 50, encourage them to choose 2 cards, make a 2 digit number and represent the number with cubes. Then determine how many more cubes they need to get to 50 and choose the 2 cards that will get closest to that number.
Representation: Internalize Comprehension.
Begin by asking, “Do you remember the game, ‘How Close?’” Invite students to recall strategies that helped them work within 20. Ask them to think about how the game will change when the target is 50.
Supports accessibility for: Memory, Attention, Organization
Required Materials
Materials to Gather
Number cards 0–10
Materials to Copy
How Close? Stage 3 Recording Sheet
Launch
Groups of 2
Give one set of digit cards to each group.
“Today we are going to play another game of How Close. This time we will play Close to 50.”
Display the digit cards at the top of the student page.
“We start with 7 cards again. Think about what cards you would choose to make 2 two-digit numbers that have a sum close to 50.”
1 minute: quiet think time
2-3 minutes: partner work time
Share responses.
“After you make your two-digit numbers, you will write an equation showing the sum.”
Demonstrate writing an equation on the recording sheet.
“Now, we see whose sum is closer to 50. Talk to your partner about how you could figure it out.” (You can count up or back from 50 and see whose number is closer.)
30 seconds: quiet think time
1 minute: partner discussion
“Then you will replace the cards you used and play again.”
Activity
"Now play How Close with your partner."
10 minutes: partner work time
Student Facing
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Activity Synthesis
Display digit cards from the student page.
“Diego made the number 38. What number could Diego make next to get close to 50?”


aligns: no