1. NOTES Multiplying Decimals MULTIPLYING DECIMALS: 1 st MULTIPLY AS NORMAL 2 nd Count the number of digits behind the decimal in the factors (in the problem) 3 rd That is how many numbers should be behind the decimal in your answer Name: ___________Date: __________ Math ___ hrMC2 pg 65 section 2.3

2. EXAMPLE 1 Multiplying Decimals 582 2 3 8 6 2 5.82 0.41 23280 2 decimal places + 2 decimal places 4 decimal places.

3. EXAMPLE 2 a.a. 6.45 5160 1 1 6 1 0 18 2 decimal places ANSWER 6.45 18 = 116.1 6450 + 0 decimal places Multiplying Decimals.

4. EXAMPLE 2 b.b. 1.273 0.06 3 decimal places 5 decimal places ANSWER 1.273 0.06 = 0.07638 + 2 decimal places 7638 Multiplying Decimals 0. 07638

5. EXAMPLE 2 GUIDED PRACTICE for Examples 1 and 2 I am giving you the digits that are in your answer. PLACE THE DECIMAL. 1. 1.4 7.2 = 1 0 0 8 10. 08 ANSWER 2. 0.98 * 0.21 = 2 0 5 8 0. 2058 ANSWER 3. 2.351 * 1.6 = 3 7 6 1 6 3. 7616 ANSWER

6. EXAMPLE 3 Finding Area Finding Area with Decimals Central Park Central Park, in New York City, is a rectangular park about 2. 5 miles long and about 0. 5 mile wide. What is the area of Central Park? SOLUTION A = l * w = 2.5 * 0.5 = 1.25 Write formula Write formula for area of a rectangle. Substitute Substitute 2.5 for l and 0.5 for w. Solve! Solve! Multiply. The area of Central Park is about 1. 25 square miles. ANSWER L= 2.5 mi W= 0.5 mi

7. EXAMPLE 3 GUIDED PRACTICE for Example 3 Find the area of the rectangle. 7. ANSWER 18.84 in. 2 8. ANSWER 36.12 cm 2 A = L * W A = 9.42 * 2 A = L * W A = 8.4 * 4.3 A = 3 6 1 2 A = 1 8 8 4

8. EXAMPLE 3 GUIDED PRACTICE EXAMPLE 4 Standardized Test Practice STEP 1 Calculate the least possible cost by using $.25 as the price for all of the fruits and vegetables. C = 14.4 0.25 = $ 3.60 SOLUTION

9. EXAMPLE 3 GUIDED PRACTICE EXAMPLE 4 STEP 2 Calculate the greatest possible cost by using $2.10 as the price for all of the fruits and vegetables. C = 14.4 2.10 = $ 30.24 ANSWER The least cost for food is $3. 60 and the greatest cost is $30.24. The correct answer is C. A B C D Standardized Test Practice

10. EXAMPLE 3 GUIDED PRACTICE EXAMPLE 3 GUIDED PRACTICE for Example 4 ANSWER $4.20 to $35.28 In Example 4, suppose you buy 16.8 pounds of fruits and vegetables. What is the range of the amount you might spend? What If? 9.

11. EXAMPLE 2 GUIDED PRACTICE 4. 2.6 m Evaluate the expression when m = 3.26 and n = 1.24. 8.476 ANSWER 5. 1.7 n 2.108 ANSWER 6. mn 4.0424 ANSWER for Examples 1 and 2

12. MULTIPLYING DECIMALS: 1 st MULTIPLY AS NORMAL 2 nd Count the number of digits behind the decimal in the factors (numbers in the problem) 3 rd That is how many numbers should be behind the decimal in your answer Name: ___________Date: __________ Math ___ hrMC2 pg 65 (2-7all, 9-20 evens, 25-28 all, 29-34 evens)