2. Lesson Menu Main Idea and New Vocabulary Example 1:Estimate by Rounding Dividends Example 2:Estimate by Rounding Divisors Example 3:Real-World Example Example 4:Real-World Example

3. Main Idea/Vocabulary Estimate the quotient of decimals and judge the reasonableness of the results. compatible numbers

4. Example 1 Estimate by Rounding Dividends Estimate 44.2  9. Using multiples of 9, 44.2 is closest to 45. Answer: The quotient is about 5.

5. Example 1 CYP Estimate 58.8  6. A.48 ÷ 6 = 8 B.54 ÷ 6 = 9 C.60 ÷ 6 = 10 D.66 ÷ 6 = 11

6. Example 2 Estimate 72  8.3. Estimate by Rounding Divisors Round 8.3 to 8 since 72 and 8 are compatible numbers. Answer: So, 72 ÷ 8.3 is about 9.

7. Example 2 CYP A.60 ÷ 6 = 10 B.54 ÷ 9 = 6 C.60 ÷ 12 = 5 D.60 ÷ 10 = 6

8. Example 3 MAMMALS The average weight of a Florida panther is 64.2 kilograms. The average weight of a coyote is 14.8 kilograms. About how many times heavier is the panther? Explain why your answer is reasonable. Round 14.8 to 15 and 64.2 to 60 since 15 and 60 are compatible numbers.

9. Example 3 Answer: The panther is about 4 times heavier than the coyote. Check for ReasonablenessSince 4 × 15 = 60 and 60 is close to 64.2, the answer is reasonable.

10. Example 3 CYP PUPPIES In a study, the average weight of a 6-week old male Labrador Retriever puppy was 5.63 kilograms. The average weight of the same puppies at 20 weeks old was 17.89 kilograms. By about how many times did the average weight increase from 6 to 20 weeks old? A.about 2 times B.about 3 times C.about 4 times D.about 5 times

11. Example 4 TRAVEL The Chu family drove 163.35 miles in 4 hours. Estimate the average number of miles they drove each hour. Justify your answer. Round 163.35 to 160. Answer: The Chu family drove about 40 miles each hour. Check for ReasonablenessSince 40 × 4 = 160 and 160 ≈ 163.35, the answer is reasonable.

12. Example 4 CYP GAS MILEAGE The Mays family drove 148.5 miles using 5 gallons of gas. Estimate the number of miles they drove for each gallon of gas. A.about 20 miles B.about 30 miles C.about 50 miles D.about 450 miles