Loading...
Estimating Fraction Sums
Lesson 4 of 8
Objective: SWBAT estimate fraction sums.
Do Now
Prior to this lesson, students learned about Estimating Fractions. The Do Now is a review of the lesson and an introduction to the lesson of estimating fraction sums.
Estimate each fraction using a benchmark.
1. 2/9
2. 1 3/5
3. 11/20
4. 2 7/10
After about 5 minutes we will review the answers. I will randomly select students to come up to the board to explain and show how they estimated each fraction. I am looking for students to explain the benchmark they used and why.
Hook
As an introduction to the lesson, I will share a story with students.
Every Sunday I go grocery shopping for the week. I am on a budget, which I have estimated the amount of money that I will spend throughout the week. For example, I've estimated that I will spend $40 this week on gas. Last Sunday before I went grocery shopping, I went to the bank to take out the $100 cash I budgeted for groceries. After, I went to the supermarket and found all the items on my list. When I checked out, my total came to $127. I didn't have enough money on me. I hadn't estimated enough money to pay for my groceries that week.
Vocabulary Review
Students may already be familiar with the terms overestimate and underestimate. Before revealing the definitions, I will ask students to share their thoughts of what it means to overestimate and underestimate and when they may be useful.
What does it mean to overestimate?
Students may give answers like:
 to round up
 to estimate high
 to estimate over what the answer is
After several students have shared their thoughts, I will give them the formal definition.
Overestimate  to give an estimate that is larger than the actual value
What are some situations where you might overestimate?
Students may give answers like:
 when you're buying supplies
 when you need money for shopping
 food for a party
What does it mean to underestimate?
Students may give answers like:
 to round down
 to estimate too low
 to estimate below what the answer is
After several students have shared their thoughts, I will give them the formal definition.
Underestimate  to give an estimate that is smaller than the actual value
What are some situations where you might underestimate?
Students may give answers like:
 when guessing someone's age or weight
 someone's abilities
Mini Lesson
I will work through a few examples with students.
Ex. 1  Estimate 1 5/6 + 1 7/8
How can we estimate the sum without finding the actual sum? What benchmarks should you use? Is this an overestimate or an underestimate?
Once students have estimated the sum, I want them to think about the type of situations we discussed. What if you were buying fencing for a garden with these lengths, would you want to overestimate or underestimate?
Ex. 2  Estimate 5 1/11 + 23 2/8 + 4/17
Is this an overestimate or an underestimate?
Independent Practice
Students will have 5 minutes to estimate the sums of the fractions below.They will determine if the sum is an overestimate or an underestimate. After 5 minutes, students will discuss their strategies and answers with their group.
As students work I will circulate throughout the room assessing students for understanding and answering their questions. If a student is struggling, I will suggest that they look back at the number lines we created in the Estimating Fractions lesson.
Estimate the sum using whole numbers. Explain if it is an overestimate or underestimate.
1.

– 

2.

+ 

3.

+ 

4.

– 

Lesson Review
I will complete the lesson by reviewing the concepts of overestimation and underestimation with students. I will randomly select students to share their thoughts.
How do you know if you have an overestimate or an underestimate? What information does it give you?
 UNIT 1: First Week of School
 UNIT 2: Properties of Math
 UNIT 3: Divisibility Rules
 UNIT 4: Factors and Multiples
 UNIT 5: Introduction to Fractions
 UNIT 6: Adding and Subtracting Fractions
 UNIT 7: Multiplying and Dividing Fractions
 UNIT 8: Algorithms and Decimal Operations
 UNIT 9: MultiUnit Summative Assessments
 UNIT 10: Rational Numbers
 UNIT 11: Equivalent Ratios
 UNIT 12: Unit Rate
 UNIT 13: Fractions, Decimals, and Percents
 UNIT 14: Algebra
 UNIT 15: Geometry
 LESSON 1: Fractions Review: Simplifying Fractions
 LESSON 2: Improper Fractions and Mixed Numbers
 LESSON 3: Estimating Fractions
 LESSON 4: Estimating Fraction Sums
 LESSON 5: Estimating Fraction Sums in Word Problems, Day 1
 LESSON 6: Estimating Fraction Sums in Word Problems, Day 2
 LESSON 7: Writing an Estimation Word Problem, Day 1
 LESSON 8: Writing an Estimation Word Problem, Day 2