1. Core Focus on Decimals & Fractions Multiplying by 2-Digit Numbers Lesson 2.1

2. 1.6  9 2.10  4 3.Janet had 5 groups of children at her house. There were 3 children in each group. How many children were at her house? 4.Henry bought 8 boxes of candy bars. Each box had 7 bars in it. How many candy bars did Henry have? Warm-Up 54 40 15 children 56 candy bars

3. Multiplying by 2-Digit Numbers Find products of expressions involving multi-digit whole numbers. Lesson 2.1

4. Vocabulary Factors Two or more numbers that can be multiplied together to find a product. Product The answer to a multiplication problem. Algorithm A process that gives steps for calculating values. The standard algorithm for multiplication gives steps for finding products. 28  4 = 112OR28  4 112 factors product

5. Example 1 What is the product of 18 and 5? Write the problem vertically with the largest factor on top. Line up by place value. Multiply the ones: 5  8 = 40. Regroup (40 = 4 tens + 0 ones) and carry the 4 tens to the tens column. Record the 0 ones. TensOnes 1  8585 TensOnes 4 1  8585 0 The 4 is from 40. The 0 is from 40.

6. Example 1 Continued… What is the product of 18 and 5? Multiply the tens: 5  10 = 50 Add the tens that were carried. 5 tens (50) + 4 tens (40) = 90. Record the 9 tens. 18  5 = 90 TensOnes 4 1  8585 0 The 9 is from 90. 9

7. Standard Algorithm for Multiplication 1.Multiply right to left. Start with the ones column and move to tens column (and so on). 2.Regroup when possible. 3.Add any partial products to find the final product.

8. Example 2 Tatiana loaded boxes of books into a warehouse. She loaded 38 boxes per hour for 24 hours this week. How many boxes of books did she load into the warehouse this week? Write the problem vertically with the largest number on top. Line up by place value. Multiply the ones (4 from 24 by the 8 from 38). 4  8 = 32 Regroup (32 = 3 tens and 2 ones) and carry the 3 tens to the tens column. Record the 2 ones. HundredsTensOnes  3232 8484 HundredsTensOnes 3  3232 8484 2

9. Example 2 Continued… Tatiana loaded boxes of books into a warehouse. She loaded 38 boxes per hour for 24 hours this week. How many boxes of books did she load into the warehouse this week? Multiply the ones from the second factor by the tens from the first factor: (4 from 24 by the 3 from 38) 4  3 tens (30) = 120 (12 tens) Add the tens that were carried. 3 tens (30) + 12 tens (120) = 150 Record the 5 tens. Carry 1 hundred and bring down. HundredsTensOnes 3  3232 8484 2 1 1 5

10. Example 2 Continued… Tatiana loaded boxes of books into a warehouse. She loaded 38 boxes per hour for 24 hours this week. How many boxes of books did she load into the warehouse this week? Multiply the tens from the second factor by the ones from the first factor (2 from 24 by the 8 from 38) 2 tens (20)  8 = 160 (1 hundred and 6 tens). Record the 6 tens. Carry the 1 hundred. HundredsTensOnes 3  3232 8484 152 1 6 0 There are no ones. Record a 0 in the ones answer column.

11. Example 2 Continued… Tatiana loaded boxes of books into a warehouse. She loaded 38 boxes per hour for 24 hours this week. How many boxes of books did she load into the warehouse this week? Multiply the tens from the second factor by the tens from the first factor: (2 from 24 by the 3 from 38). 2 tens (20)  3 tens (30) = 600 (6 hundreds) Add the hundred that was carried. Add the two partial products together. Tatiana loaded 912 boxes of books into the warehouse this week. HundredsTensOnes 13  3232 8484 152 +60 7 152 + 760 912

12. Communication Prompt What methods have you used in the past for multiplying? What method of multiplying do you like best?

13. 1.45  13 2.Noe made $12 per hour. He worked 26 hours this week. How much did Noe make this week? 3.Martin jumped rope for 35 minutes each day. After 14 days, how many minutes did Martin jump rope in all? Exit Problems 585 $312 490 minutes