Illuminations: How Many More Fish?

How Many More Fish?


Wrapping Up the Unit

During this final lesson in the unit, the students use the mathematical knowledge and skills developed in the previous lessons as they visit five stations to review comparative subtraction.

Learning Objectives

 
Students will:
  • review the meanings for subtraction
  • practice comparative subtraction in a variety of formats

Materials

 
Fish-shaped crackers in resealable bags
Index cards
Paper plates
Paper and Crayons
Number cubes
Pennies
Cups
Number Lines Activity Sheet
Adjustable Spinner

Instructional Plan

Assign groups of four students each to work at one of the five stations. If you need more than five stations, you might choose to provide an extra computer for a sixth station.]

Station 1: High versus Low

Materials: Twelve index cards, numbered 0 through 11

Place the cards upside down in a stack in the center of the group and ask each student to draw one and place it face up where all can see it. To play, the students should order the cards from least to greatest, then find the difference of the highest and lowest card. The students who drew the highest and lowest cards record a tally mark, and all players return their cards to the deck that is then shuffled. Play continues until one student has five tally marks or time is up.

 

Station 2: How Many More?

Materials: fish-shaped crackers, paper, paper plates, number cubes

Each student rolls the dice and makes a plate that has as many fish-shaped crackers as the sum of the numbers thrown on the dice. Then the students compare the plates. The player with the plate with the most crackers finds the difference between the number of crackers on his or her plate and those of each of the other three plates, then makes a tally mark on a piece of paper. When time is up, the student with the most tallies wins the game.

 

Station 3: Spin, Spin, Spin

Materials: Adjustable Spinner, paper

[Before class, divide the Adjustable Spinner into 12 parts.] Direct the group to take turns spinning the spinner twice and recording the numbers. When all have recorded two numbers, ask them to subtract the smaller from the greater number. Then ask them to see whether anyone got a difference larger than everyone else. If so, that student wins a point. The student who has earned the most points when time is called wins the game.

 

Station 4: Heads or Tails?

Materials: 20 pennies, cup

Divide the group of four into teams of two. Give each team a cup containing 10 pennies. Assign one team to count heads and the other to count tails. Have the teams empty their cups onto the table. Then the teams count how many of the 20 pennies came up with their assigned side. The team with more announces how many more heads or tails in their set of coins and records that amount on a score sheet. The first team to reach or pass 25 wins the game.

 

Station 5: What a Difference

Materials: Four number cubes, Number Lines Activity Sheet, fish-shaped crackers

Divide the group of four into two teams of two. Give each team of players some crackers, a number line, and two dice. Tell the teams to take turns rolling the 2 dice and place a cracker on the number line that matches the larger number rolled. Have students place a cracker on the smaller number rolled. Then ask students to compare the places they landed on by finding the difference. Ask them to record the differences they found and repeat the activity. When time is nearly up, ask the teams to tally the total of differences from each play.

 

After each 10-minute interval has passed, assign the students to new stations. When time is up, call them together and ask students to record in their journals which station they liked most and why. Explain to students that they should focus on the mathematics they learned from each station rather than on other aspects of the activity.

Questions for Students

 

What addends less than 10 have differences of 2? Of 5?

What subtraction sentence shows that we have compared a set of seven red pencils with a set of five blue pencils?

A balance has three crackers of the right side and five on the left side. Which side needs more crackers? How many more?

How could you use a number line to compare a plate of eight fish-shaped crackers with a plate of five fish-shaped crackers?

If you subtract 0 from a number, what happens?

What are the addition facts and the subtraction facts in one family where the sum is 6? When the sum is 8?

How did you use subtraction in the games that you played? What activity did you like most? Which was hardest for you? Why?

Assessment Options

 
  1. You may wish to review the completed Class Notes recording sheets completed throughout this unit. These can guide the summative comments you make for individual students.

Teacher Reflection

 
  • With what meanings of subtraction were the majority of the students most comfortable?
  • Did all the students display understanding of the subtraction meanings?
  • Can the students explain how to compare to find differences?
  • Which students met all the objectives of this unit? What extension activities are appropriate for those students?
  • Which students are still having difficulty with the objectives of this unit? What additional instructional experiences do they need?
  • What were the greatest challenges for the students?
  • What will I do differently the next time that I teach this unit?
  • What other learning situations would extend their experiences with comparison subtraction?
  • How might I connect the essential ideas of this unit with lessons about related mathematics content? (Data is an area that is a logical extension of this unit.)

NCTM Standards and Expectations

 
Number & Operations Pre-K-2
  1. Develop understanding of the relative position and magnitude of whole numbers and of ordinal and cardinal numbers and their connections.
  2. Count with understanding and recognize "how many" in sets of objects.
  3. Use multiple models to develop initial understandings of place value and the base-ten number system.
  4. Understand the effects of adding and subtracting whole numbers.
  5. Understand various meanings of addition and subtraction of whole numbers and the relationship between the two operations.
  6. Develop and use strategies for whole-number computations, with a focus on addition and subtraction.
  7. Develop fluency with basic number combinations for addition and subtraction.
  8. Use a variety of methods and tools to compute, including objects, mental computation, estimation, paper and pencil, and calculators.
This lesson prepared by Grace M. Burton.
  
1 period   

NCTM Resources

Navigating through Number in preK‑2

 Activities


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