# Lesson: Fractions: Sum and Difference

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### Lesson Objective

SWBAT model fraction sums and differences with pattern blocks.

### Lesson Plan

Materials Needed: scrap paper for DN, white board, dry erase markers, pencils, pattern-block sets for each student [trapezoids (x2), rhombuses (x2), and triangles (x6), hexagon (x2)], and IND Worksheet.
Vocabulary: whole (or ONE or unit), denominator, numerator, hexagon, trapezoid, rhombus, and triangle.

……….
Do Now (2 -3 min): One the board the teacher writes the following: 1/20; 9/10; 48/50; 5/8; 3/16; 8/15. The students should be directed to indicate whether each fraction is closest to 0, ½ , or 1 and give an explanation of their answer.

Opening (2 -3 min): Teacher quickly reviews the answer to the Do Now and has students share their thinking or strategy for finding the answer. Then the teacher should state the objective, “Yesterday, we found fractions parts of shapes. Today, we are going to focus on fraction sums and differences. By the end of this lesson, you will be able to model fraction sums and differences with pattern blocks.”

Direct Instruction (10 min): Teacher begins by telling the students, that “In this lesson they will used pattern blocks, like the ones used yesterday, to model fraction addition and subtraction problems.  The teacher then introduces using the pattern blocks on an overhead projector or by using magnetic tape. The teacher will model one fraction addition problem for the class.

2/3 + 1/6 = ________[5/6]

The teacher should follow the following steps when explaining this to the students.

1. Use the pattern blocks to model the fractions to be added.
2. Combine the blocks to show the sum
3. Trade the blocks in the sum for blocks of a single type
4. Name the fraction for the sum.

The example is explained in the Chart Example_Fraction Sum/Difference.

The teacher should then model an additional example for the students using the pattern blocks.

1/3 + ½ = ? [5/6]

The teacher should then model a difference problem for the students using the same strategy. Please look at the Chart Example_Fraction Sum/Difference for procedures. The teacher should ask the students how they could use pattern blocks to solve 5/6 – 2/3 =

The steps for the Take Away Method are as follows:
1. Model the larger fraction with pattern blocks
2. Remove blocks representing the smaller fraction.
3. The block (s) that are left represent the difference

Guided Practice (10 min): The teacher should then complete the following problems with the class using the overhead.

Sum:
1/3 + 1/2=_________________[5/6]
4/6 + 1/3=_________________[6/6 or 1]

Difference:
2/3 – ½ =_______________[1/6]
2/3- 1/6 =_______________[3/6 or ½]

Independent (10 min):  The teacher then calls the students attention toward him/her before beginning IND work. The teacher passes out the IND Worksheet. The students are to hand in the IND Worksheet when finished.

Closing (2-3 min): Teacher calls the attention of the students back toward the front of the class to quickly review the answers to the Independent Practice worksheet/ ask what we learned about.

### Lesson Resources

 IND Worksheet Lesson 6   Classwork Chart Example Sum and Difference   Exemplar