5th Grade Module 2 – Lesson 2 Lesson 2: I can estimate multi-digit products by rounding factors to a basic fact and using place value patterns. 5th Grade Module 2 – Lesson 2

5th Grade Module 1 – Lesson 5 Time to Sprint! Your teacher will give you today’s sprint. 5th Grade Module 1 – Lesson 5

Get Your White Board Ready! Time to Round! 48,625 Round to nearest ten-thousand Say the Number! Between which two ten-thousands is 48,625? Draw & label a number line What is the midpoint for 40,000 & 50,000? Where would 48,625 fall? Above or below the midpoint? 40,000 50,000 48,625 What is 48,625 rounded to the nearest ten-thousand? 45,000 50,000 5th Grade Module 2 – Lesson 2

48,625 Round to nearest thousand Say the Number! Between which two thousands is 48,625? Draw & label a number line What is the midpoint for 48,000 & 49,000? Where would 48,625 fall? Above or below the midpoint? 48,000 49,000 What is 48,625 rounded to the nearest thousand? 48,625 49,000 48,500 5th Grade Module 2 – Lesson 2

48,625 Round to nearest hundred Say the Number! Between which two hundreds is 48,625? Draw & label a number line What is the midpoint for 48,700 & 48,600? Where would 48,625 fall? Above or below the midpoint? What is 48,625 rounded to the nearest hundred? 48,600 48,700 48,600 48,650 48,625 5th Grade Module 2 – Lesson 2

48,625 Round to nearest ten Say the Number! Between which two tens is 48,625? Draw & label a number line Where would 48,625 fall? Above or below the midpoint? What is the midpoint for 48,620 & 48,630? 48,620 48,630 What is 48,625 rounded to the nearest ten? 48,630 48,625 48,625 5th Grade Module 2 – Lesson 2

Get Your White Board Ready! Record & Solve 31 x 10 = ______ 310 310 x 2 = ______ 620 31 x 10 x 2 = 620 3-step multiplication sentence 310 x 20 = ______ Solve as a three-step multiplication sentence, taking out the ten 310 x 10 x 2 = 6,200 5th Grade Module 2 – Lesson 2

Solve using a multi-step multiplication sentence, taking out the tens. 23 x 40 23 x 10 x 4 230 x 4 23 x 4 x 10 92 x 10 OR 23 x 40 = 920 5th Grade Module 2 – Lesson 2

Solve using a multi-step multiplication sentence, taking out the tens. 32 x 30 32 x 10 x 3 320 x 3 32 x 3 x 10 96 x 10 OR 32 x 30 = 960 5th Grade Module 2 – Lesson 2

5th Grade Module 2 – Lesson 2 Application Problem Jonas practices guitar 1 hour a day for 2 years. Bradley practices the guitar 2 hours a day more than Jonas. How many more minutes does Bradley practice the guitar than Jonas over the course of 2 years? 5th Grade Module 2 – Lesson 2

5th Grade Module 2 – Lesson 2 Concept Development We are going to learn how to use estimation to help us find a product. Estimates can help us understand a reasonable size of a product when we multiply the original numbers. Let’s figure out about how many students we have at Eureka Elementary. First, let’s use the number of students we have in our class to help us. How many students are in our class? Then, let’s think how many classrooms we have in our school. How many classrooms? If we have 22 students in our class and we have 18 classrooms. What could I do to find a number that is close to the actual number of students in our school? In order to “estimate” the total number of students we can round each number so it will be easier to multiply mentally. Let’s round 22 to 20 and let’s round 18 to 20. We can now multiply 20 by 20 5th Grade Module 2 – Lesson 2

Let’s practice how we can use rounding to estimate the product. About 20,000 456 x 42 ≈______ How can I round these factors to estimate the product? Remember, we want to be able to multiply mentally. Which is the easier way to solve this? 460 x 40 or 500 x 40 What would the estimate be? Solve in unit form: 2. Solve in standard form: 5 hundreds x 4 tens = 20 thousands (5 x 100) x (4 x 10) = (5 x 4) x (100 x 10) = 20 x 1,000 = 20,000 5th Grade Module 2 – Lesson 2

Let’s estimate the product of two more problems… Remember to think which rounded value would be the easiest to mentally multiply! 4,560 x 42 ≈ ______ 200,000 5000 x 40 = 200,000 (5 x 4) x (1000 x 10) 20 x 10,000 4,560 x 420 ≈ ______ 2,000,000 5000 x 400 = 2,000,000 (5 x 4) x (1000 x 100) 20 x 100,000 5th Grade Module 2 – Lesson 2

13,205 x 880 ≈ ______ 1,320 x 88 ≈ ______ What if we change it to: Problems 5-7 Round the factors to estimate the product: 1,320 x 88 ≈ ______ Let’s share some of your thinking. Option 2: 1,300 x 90 = (13 x 9) x (100x 10) 117 x 1,000 117,000 Either option is acceptable. Option 1 is the easiest. Option 2 is closer to the actual. Why? Option 1: 1,000 x 90 = 90,000 What if we change it to: 13,205 x 880 ≈ ______ Let’s test our predictions. Round and find the estimate product. What is different from the problem above? What do you think will change about our estimate? 10,000 x 900 ≈ (1 x 9) x (10,000 x 100) 9 x 1,000,000 9,000,000 Was our prediction accurate? Yes! 9 million is 100 times as large as 90,000! 5th Grade Module 2 – Lesson 2

Work with your partner to estimate the following problems. 3,120 x 880 31,200 x 880 Volunteers to show their answers: 5th Grade Module 2 – Lesson 2

Get Ready to Complete the Problem Set on Your Own! Complete Pages 2.A.23 & 2.A.24 You will have 10-15 minutes to work. Try your Best! 5th Grade Module 1 – Lesson 5

5th Grade Module 1 – Lesson 5 LET’S Debrief 5th Grade Module 1 – Lesson 5

5th Grade Module 1 – Lesson 5 EXIT TICKET 5th Grade Module 1 – Lesson 5