1. Course 1 1-6 Choose the Method of Computation 1-6 Choose the Method of Computation Course 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day

2. Course 1 1-6 Choose the Method of Computation Warm Up Use mental math to find each fraction of 80. 1. 2. 3. 4. 40 8 20 1 10 __ 1 2 16 1 4 1 5

3. Course 1 1-6 Choose the Method of Computation Problem of the Day About 23% of 600 firefighters are not on duty on any particular day. Steven estimates that about 200 firefighters have the day off. Is his estimate too high or too low? Explain. too high; 25% of 600 is 150

4. Course 1 1-6 Choose the Method of Computation Learn to choose an appropriate method of computation and justify your choice.

5. Course 1 1-6 Choose the Method of Computation Additional Example 1A Evaluate the expression and state the method of computation you used. There are probably too many numbers to add mentally, but the numbers are small. You can use paper and pencil. 35 4 + 3 + 2 + 10 + 8 + 2 + 5 + 1

6. Course 1 1-6 Choose the Method of Computation Additional Example 1B Evaluate the expression and state the method of computation you used. 4,562 – 397 397 is close to a multiple of 100. You can use mental math. (4,562 + 3) – (397 + 3) 4,565 – 400 4,165 Think: Add 3 to 397 to make 400. Add 3 to 4,562 to compensate.

7. Course 1 1-6 Choose the Method of Computation Additional Example 1C Evaluate the expression and state the method of computation you used. 9,288 ÷ 24. The numbers are not compatible, so mental math is not a good idea. You could use paper and pencil, but long division requires several steps. Using a calculator will probably be faster. 387

8. Course 1 1-6 Choose the Method of Computation It might be hard to keep track of all of these numbers if you tried to add mentally. But the numbers themselves are small. You can use paper and pencil. 42 Check It Out: Example 1A Evaluate the expression and state the method of computation you used. 3 + 7 + 2 + 18 + 7 + 1 + 3 + 1

9. Course 1 1-6 Choose the Method of Computation Check It Out: Example 1B Evaluate the expression and state the method of computation you used. 3,442 – 298 298 is close to a multiple of 100. You can use mental math. (3,442 + 2) – (298 + 2) 3,444 – 300 3,144 Think: Add 2 to 298 to make 300. Add 2 to 3,442 to compensate.

10. Course 1 1-6 Choose the Method of Computation Check It Out: Example 1C Evaluate the expression and state the method of computation you used. 9,248 ÷ 32. The numbers are not compatible, so mental math is not a good idea. You could use paper and pencil, but long division requires several steps. Using a calculator will probably be faster. 289

11. Course 1 1-6 Choose the Method of Computation Lesson Quiz Evaluate the expression and state the method of computation you used. 1. 17 + 6 + 24 + 35 + 3 + 5 2. 63  197 3. It takes Jupiter approximately 4,344 days to complete one revolution around the Sun. It takes Earth 365 days to revolve around the Sun. How many more days does it take Jupiter to revolve around the Sun than Earth? 12,411; paper and pencil 90; mental math 3,979 days