today we will discuss about the topic: multiply 2-4 digit by 1 digit

CONFIDENTIAL 1

Today we will discuss about the topic:

Multiply 2-4 digit by 1 digit

Good Afternoon!

Let’s Warm up:.

1) 3 x 4 = 2) 12 x 3 =

5) Find out the value of 2x2 with the help of the model given below?

3) 5 x 5 = 4) 6 x 6 =

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REVIEWLet’s discuss what we did in the last session.

We learnt about the following terms:

Multiple: It is the product of a number and any whole number.

Even numbers: Whole numbers that are divisible by 2 are even numbers.

Odd numbers: Whole numbers that are not divisible by 2 are odd numbers.

Prime numbers: Numbers whose factors are only 1 and the number itself are prime numbers.

Composite numbers: All the non-prime numbers except 0 and 1, are Composite Numbers.

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We can multiply by the means of Skip Counting also.

By Skip Counting we mean that we can find the multiples of any number by hopping equal steps on the

number line.

0 1 2 3 4 5 6

2 2 2 Here the numbers are

taking 3 jumps each of

2 steps.

REVIEW

CONFIDENTIAL 4

There are other strategies that can be used for multiplication.

Find 7 x 3.

Use a Known Fact

7 groups of 3 = 7 groups of 2 plus 7

7 x 3 = 7 x 2 + 7 = 14 + 7 = 21

Double a Known Fact

Find 8 x 6.

8 x 6 = (4 x 6 ) + (4 x 6)

= 24 + 24 = 48

8 groups of 6 = 4 groups of 6 + 4 groups of 6

REVIEW

CONFIDENTIAL 5

We looked into the Multiplication Table and its patterns :

x 0 1 2 3 4 5 6 7 8 9 10 11 12

0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 0 1 2 3 4 5 6 7 8 9 10 11 12

2 0 2 4 6 8 10 12 14 16 18 20 22 24

3 0 3 6 9 12 15 18 21 24 27 30 33 36

4 0 4 8 12 16 20 24 28 32 36 40 44 48

5 0 5 10 15 20 25 30 35 40 45 50 55 60

6 0 6 12 18 24 30 36 42 48 54 60 66 72

7 0 7 14 21 28 35 42 49 56 63 70 77 84

8 0 8 16 24 32 40 48 56 64 72 80 88 96

9 0 9 18 27 36 45 54 63 72 81 90 99 108

10 0 10 20 30 40 50 60 70 80 90 100 110 120

11 0 11 22 33 44 55 66 77 88 99 110 121 132

12 0 12 24 36 48 60 72 84 96 108 120 132 144

In the table, the pattern of the square numbers are shown within the yellow

squares.

CONFIDENTIAL 6

Today we will learn to Multiply 2-4 digit by 1 digit

Multiplication is an operation on two numbers to find a product. Like 3 x 4 = 12.

ASSOCIATIVE PROPERTY:

While multiplying, we can change the grouping of the factors and the product stays the same.

EXAMPLE: 2 x (3 x 4) = (2 x 3) x 4 2 x (3 x 4) = 2 x 12 =

24 (2 x 3) x 4 = 6 x 4 =24

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Uses of the ASSOCIATIVE PROPERTY:

Find: 2 x 6 x 4

Here, Associative Property of Multiplication can be used to multiply the three factors. We will see that the

grouping of the numbers does not affects the answer.

STEP 1:

Use parentheses to show the grouping.

2 x 6 x 4 = (2 x 6) x 4

CONFIDENTIAL 8

STEP 2:

Look for a known fact to multiply. 2 x 4 is a known fact.

STEP 3:

Use the Commutative Property to change the order, if necessary.

(2 x 6) x 4 = 2 x (6 x 4)

= 2 x 24 = 48

Therefore, the product of 2 x 6 x 4 is 48.

CONFIDENTIAL 9

You can use pattern of factors and products to multiply mentally.

3 x 2 = 6

3 x 20 = 60

3 x 200 = 600

3 x 2,000 = 6,000

Multiply: 4 x 3 x 7

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We multiply numbers by first lining up the digits in the following manner:

Find: 236 x 6

236X 6

First multiply 6 with 6 to obtain 36.

6

3

STEP 1:

Regroup 36 as 3

tens and 6 ones.

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236X 6

Again, multiply 6 with 3 at the tens place to obtain 18.

Then, add 3 and 18 to obtain 21.

16

23

STEP 2:

Regroup 21 as 2

hundreds and 1 tens.

CONFIDENTIAL 12

236X 6

Then, multiply 6 with 2 at the hundreds place to obtain 12.

Then, 2 and 12 to obtain 14.

1416

23

STEP 3:

Hence, the

result.

Multiply: 564 x 3

CONFIDENTIAL 13

Estimating Products:

Estimate 6 x 44.

By Estimate, we mean an answer that is close to the exact answer.

While estimating products, we round the greater factor.

6 x 44.

6 x 40 =240

Round to the

nearest tens.

Hence, the estimated value of 6 x 44 is 240.

CONFIDENTIAL 14

There are two terms related to Estimation.

Overestimate: It is an estimate greater than the exact answer.

Underestimate: It is an estimate less than the exact answer.

Example: Estimate: 5 x 36

5 x 36 = 180

5 x 40 = 200

200 > 180

Round 36.

Example: Estimate: 5 x 33

5 x 33 = 165

5 x 30 = 150

150 < 165

Round 33.

CONFIDENTIAL 15

We can do multiplication by other methods also.

Multiply: 5 x 3,839

Here we use the Distributive Property to multiply 5 x 3,839

Split 3,839 into 4 parts:3,000 + 800 + 30 + 9

Here, we see that the greater factor is converted to the Expanded Form.

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Then multiply each part by 5:

5 x 3,000 =15,000

5 x 800 = 4,000

5 x 30 = 150

5 x 9 = 45

Then finally add each part:

15,000 + 4,000 + 150 + 45 = 19,195

Hence, 5 x 3,839 = 19,195.

CONFIDENTIAL 17

BREAK

CONFIDENTIAL 18

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CONFIDENTIAL 19

Assignments

Using the Associative Property of Multiplication, find the products of the

following.

1) (3 x 5) x 7 =

4) (6 x 5) x 2 =

2) (8 x 2) x 6 =

3) (4 x 7) x 4 =

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Find the product:

573X 3

924X 7

5) 6)

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Estimate the products of the given problems:

7) 6 x 44 8) 7 x 48

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Multiply using the Distributive Property :

9) 6 x 694 10) 2 x 7,295

CONFIDENTIAL 23

Multiplication is an operation on two numbers to find a product. Like 3 x 4 = 12.

ASSOCIATIVE PROPERTY:

While multiplying, we can change the grouping of the factors and the product stays the same.

EXAMPLE: 2 x (3 x 4) = (2 x 3) x 4

Very Good!Let's Review

You can use pattern of factors and products to multiply mentally.

3 x 2 = 6

3 x 20 = 60

3 x 200 = 600

3 x 2,000 = 6,000

CONFIDENTIAL 24

We multiply numbers by first lining up the digits.

236X 6

First multiply 6 with 6 to obtain 36.

6

3

STEP 1:

Regroup 36 as 3

tens and 6 ones.

236X 6

Again, multiply 6 with 3 at the tens place to obtain 18.

Then, add 3 and 18 to obtain 21.

16

23

STEP 2:

Regroup 21 as 2

hundreds and 1 tens.

CONFIDENTIAL 25

236X 6

Then, multiply 6 with 2 at the hundreds place to obtain 12.

Then, 2 and 12 to obtain 14.

1416

23

STEP 3:

Hence, the

result.

Estimate 6 x 44.

By Estimate, we mean an answer that is close to the exact answer.

While estimating products, we round the greater factor.

6 x 44.

6 x 40 =240

Round to the

nearest tens.

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Overestimate: It is estimate greater than the exact answer.

Underestimate: It is estimate less than the exact answer.

We also use the Distributive Property to multiply.

Split 3,839 into 4 parts:3,000 + 800 + 30 + 9

5 x 3,000 =15,000

5 x 800 = 4,000

5 x 30 = 150

5 x 9 = 45

Then finally add each part:

15,000 + 4,000 + 150 + 45 = 19,195

Multiply: 5 x 3,839

Then multiply each part by 5:

CONFIDENTIAL 27

You have done a nice job.See you in the next session.