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# Multiplication Using Arrays

Sep 20, 2022

## Key Concepts

• Use arrays to multiply with 3.
• Use arrays to multiply with 4.

### 3.2 Apply properties: 3 and 4 as factors

#### What is meant by factors?

A factor is a number that divides the given number without any remainder.

• The number 1 is the smallest factor of every number.
• Every number will have a minimum of two factors, 1 and the number itself.
• A number that has only two factors, 1 and the number itself, is called a prime number.

#### What are the factors of 3?

Factors of 3 are, 1 and 3

#### What are the factors of 4?

Factors of 4 are 1, 2, and 4

4 equals 2 x 2

4 = 22

Real-life applications of factors:

Dividing something into equal pieces, exchanging money, comparing prices, understanding time and making calculations.

### 3.2.1 Use arrays to multiply with 3

Example1:

Ria went to a playground. She arranged 3 rows of balls in the playground. There are 5 balls in each row. How many balls did Ria arrange?

Find 3 x 5

Solution:

Step1:  Make an array for each multiplication sentence.

3 x 5 is 3 rows of 5. That is 2 fives plus one more five.

Step2 : Multiply 2 x 5=10

Step3 : 1 x 5  =  5.

Step4 :  10+5  =  15.

Step5 : Multiply 3 x 5 =15

Ria arranged 15 balls.

Example2:

Steven arranged 3 rows of strawberries in a plate. He put 4 strawberries in each row. How many strawberries did Steven arrange in the plate?

Find 3 x 4.

Solution:

Step1:  Make an array for each multiplication sentence.

3 x 4 is 3 rows of 4. That is 2 fours plus one more four.

Step2: Multiply 2 x 4=8.

Step3 : 1 x 4  =  4.

Step4 :  8+4 =  12.

Step5 : Multiply 3 x 4 =12.

Steven arranged 12 strawberries.

### 3. 2. 2 Use arrays to multiply with 4

Example1:

Michael invited some of his friends to his house. He arranged 4 rows of cupcakes on the table for his friends. He put 5 cupcakes in each row. How many cupcakes did he arrange on the table?

Find 4 x 5

Solution

Step1: Make an array for each multiplication sentence.

4 x 5 is 4 rows of 5

That is 2 fives plus 2 fives

Step2: Multiply 2 x 5 = 10

Step3: Add 10 + 10 = 20

So, 4 x 5 = 20

The boy arranged 20 cupcakes.

Example2:

John arranged 4 rows of chairs for a meeting. He put 4 chairs in each row. How many chairs did John arrange?

Solution:

Step1: Make an array for each multiplication sentence.

4 x 4 is 4 rows of 4.

That is 2 fours plus 2 fours.

Step2: Multiply 2 x 4 = 8

Step3: Add 8 + 8 = 16

So, 4 x 4 = 16

John arranged 16 chairs for the meeting.

## Exercise:

1. Find 4 x 6

2. Multiply the following:

3. Match the following:

4. Chrissy arranged 3 rows of plants in her garden. She put 8 plants in each row. How many plants did Chrissy arrange?

5. Fill in the blanks:

a. 3 x 5=_

b. 4x_= 16

c. 3×8=_

d. 4x = 28

6. David arranged 3 rows of bananas. He put 4 bananas in each row. How many bananas did David arrange?

7. Ria saw a goat farm which has 3 pens. Each pen has 5 goats. Find the number of goats on the farm.

8. Steven walks 4 miles each day. How many miles does Steven walk in one week?

## Concept map:

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