5th Grade Module 2 – Lesson 18 Lesson 18: I can use basic facts to estimate quotients with two-digit divisors. 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Divide By Multiples of 10 12,000 ÷ 40 12,000 ÷ 10 ÷ 4 1,200 ÷ 4 300 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Divide By Multiples of 10 12,000 ÷ 400 12,000 ÷ 100 ÷ 4 120 ÷ 4 30 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Divide By Multiples of 10 12,000 ÷ 4,000 12,000 ÷ 1,000 ÷ 4 12 ÷ 4 3 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Divide By Multiples of 10 360,000 ÷ 6,000 360,000 ÷ 1,000 ÷ 6 360 ÷ 6 60 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Divide By Multiples of 10 490,000 ÷ 700 490,000 ÷ 100 ÷ 7 4,900 ÷ 7 700 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Divide By Multiples of 10 640,000 ÷ 80 640,000 ÷ 10 ÷ 8 64,000 ÷ 8 8,000 5th Grade Module 2 – Lesson 18

Estimate and Divide Say the divisor rounded to the nearest ten… Estimate the value… Name the multiple of 40 that’s closest to 812… 812 ÷ 39 ÷ 40 800 20 5th Grade Module 2 – Lesson 18

Estimate and Divide Say the divisor rounded to the nearest ten… Estimate the value… Name the multiple of 30 that’s closest to 183… 183 ÷ 31 ÷ 30 180 6 5th Grade Module 2 – Lesson 18

Estimate and Divide Estimate the value… Say the divisor rounded to the nearest ten… Name the multiple of 70 that’s closest to 420… 437 ÷ 72 ÷ 70 420 6 5th Grade Module 2 – Lesson 18

Estimate and Divide Say the divisor rounded to the nearest ten… Estimate the value… Name the multiple of 100 that’s closest to 800… 823 ÷ 97 ÷ 100 800 8 5th Grade Module 2 – Lesson 18

Estimate and Divide Say the divisor rounded to the nearest ten… Estimate the value… Name the multiple of 90 that’s closest to 8,100… 8,191 ÷ 92 ÷ 90 8,100 90 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Application Problem Sandra bought 38 DVD movies for $874. Give an estimate of the cost of each DVD movie. Solution on next slide… 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Solution $874 ÷ 38 = 800 ÷ 40 = (800 ÷ 10) ÷ 4 = 80 ÷ 4 = $20 per DVD 5th Grade Module 2 – Lesson 18

Concept Development 8,095 ÷ 23 8,095 What’s the whole (or dividend) in this problem? First, let’s round the divisor to the nearest ten! 23 ≈ 20 Let’s record our estimation below. We can round 8095 to 8000 since I can use mental math to divide 8000 by 20. Now let’s solve. Remember to take out the 10 to help you. Let’s use rounding to find an estimated quotient! 23 What’s the divisor? We need to round our whole, 8095, to a number that can easily be divided by 20. Turn and share your ideas to your partner. 8,095 ÷ 23 ≈ ____ ÷ 20 8000 8000 ÷ 10 ÷ 2 800 ÷ 2 400 5th Grade Module 2 – Lesson 18

Problem 2 2,691 ÷ 48 2,691 ÷ 48 ≈ 54 Take out your journal. Let’s estimate the quotient. What do we do first? Let’s solve. Taking out the 10 in 50. 1st – Round the Divisor 48 ≈ 50 2,691 ÷ 48 ≈ ____ ÷ 50 2700 2nd – Round the Whole (dividend) 2700 ÷ 10 ÷ 5 270 ÷ 5 Think… When we round for division we want to make sure our dividend is a multiple of the divisor. We have to think of the nearest multiple of 50. = 54 5th Grade Module 2 – Lesson 18

5,484 ÷ 71 Work with your partner and solve the estimated quotient. Problem 3 5,484 ÷ 71 Work with your partner and solve the estimated quotient. Remember we are finding the estimated quotient! Volunteer to Share Solution: Round the Divisor List the multiples of the rounded divisor to find the one that is closest to 70 Use the closest multiple as your rounded whole number. Divide using the rounded digits. Check to see if your estimated quotient makes sense. Solution on next slide… 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 Solution 5,484 ÷ 71 ≈ 5,600 ÷ 70 5,600 ÷ 10 ÷ 7 560 ÷ 7 ≈ 80 5,484 ÷ 71 ≈ 80 5th Grade Module 2 – Lesson 18

9,215 ÷ 95 Work independently to estimate the quotient. Check your work with your partner. Solution (use ink tools): 5th Grade Module 2 – Lesson 18

Get Ready to Complete the Problem Set on Your Own! Complete Pages 2.E.33 & 2.E.34 You will have 15 minutes to work. Try your Best! 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 LET’S Debrief When estimating Problem 1(g), what did you choose for your unit, 70 or 80? Why? How did it affect the way you estimated the whole? Look back at Problem 2 and 4. How was your approach similar in solving? How was it different? When solving Problem 3(b), could a mental math approach have been used? (14 apps x $2 – 14 cents) Explain. 5th Grade Module 2 – Lesson 18

5th Grade Module 2 – Lesson 18 EXIT TICKET Page 2.E.35 5th Grade Module 2 – Lesson 18