Multiplying 2-to 4-Digit Numbers by Multiplies of

10

Find the product.

a) 21 b) 122 c) 3 012 x 5 x 6

x 4

d) 4 024 e) 313 x 2 x 3

In a toy factory, a group of workers filled the 21 boxes with 50 toy cars each. How many toy cars were filled in the boxes?

What is asked? ( the total number of toy cars that were filled in all the boxes)

What are the given facts? ( 21 boxes and 50 toy cars )

What shall we do find the answer? ( multiply )

What is the number sentence for the problem? (21 x 50 = N)

Step 121

x 5000

Step 221

x 5000

105

Step 321

x 5000

105 1050

( 1 050 toy cars were filled in all boxes )

0

10 20 30 40 50 60 70 80 90 100 110 120 130

How many zeros are there in 12 tens?

How many zeros are there in 10? What did you do with zero?

12

x 10 or 12 x 10 = 120

120

a.To multiply by a multiple of 10, multiply the non-zero digits first, and then annex zeros in the product.

b.The number of zero in the factors is equal to the number of zeros in the product.

Solve the following problems:

1. There are 165 trays of oranges. Each tray has 20 oranges. How many are there in all?

2. Grade 3 SPED A class has 43 pupil. Each pupil has 10 books each. How many books did they have altogether?

3. If there are 24 bottles in a case, how many bottles will there be in 30 cases?

Exercise:1) 36

x 10

2) 25

x 20

3) 45

x 30

4) 232

x 20

5) 9 201

x 30

a. 36

a. 2 520

a. 1 350

a. 2 320

a. 276 030

b. 360

b. 2 500

b. 1 530

b. 6 420

b. 270 603

c. 3 610

c. 500

c. 1 340

d. 4 640

c. 273 060

Assignment:

A.Answer the following:1) 73 x 10 =2) 25 x 30 =3) 15 x 10 =4) 62 x 10 ( <,>,= ) 60 x 105) 43 x 20 ( <,>,= ) 53 x 10

B. Find the product:1) 77 x 10 =2) 250 x 20 =3) 2 248 x 20 =4) 1 623 x 30 =5) 4 132 x 40 =