1. Warm Up Problem
Natalie bought 12 pens for $0.59 each.
She paid with a $10 bill. How much change will she receive?

2. Multiply Decimals by Decimals
Lesson 3-4

3. Objectives I can multiply decimal numbers by decimal numbers.
I can use estimation to justify my answer.

4. Example 1
Find 3.6 x 0.05.
1) Count the number of digits to the right of the decimal point in BOTH factors. 3
2) Multiply without the decimals: 36
x 5
180
3) Add back 3 decimal places to the right.
0.180 or 0.18

5. Example 2
Find x 7.2.
Count the total number of digits to the right of the decimal. 4
Multiply:
112 x
224
+ 7840
8064
Add the decimal back with 4 places to the right:
0.8064

6. Got It?
1) 5.7 x 2.8
2) x 3.7

7. Example 3
Find 1.4 x 0.067
1) Count up the numbers to the right of the decimal. 4
2) Multiply: 67
X 14
268
+ 670
938
3) Add the decimal back. Annex a zero, if necessary.
0.0938

8. Example 4 Find 0.45 x 0.053. 1) Count up the digits to the right. 5
2) Multiply: 53
x 45
265
+ 2120
2385
3) Add the decimal back. Annex zeros, if necessary.

9. Got It?
3) 0.04 x 0.32
4) 0.26 x 0.205

10. Homework Hint #13
What do you notice about the decimal point when multiplying? X 3
0.3
0.03
0.003 4 12
1.2
0.12
0.4
0.012
0.0012
0.04
0.004