 # 4.03 Story problems

Lesson

## Ideas

Sometimes, we need to know how to write a number sentence from a  story problem  .

### Examples

#### Example 1

There were 2 rows of trees in a field, with 3 trees in each row.

Write a number sentence for this story problem to find the total number of trees in the field.

Worked Solution
Create a strategy

Since there is an equal number of trees in each row, we can think of each row as a group.

Apply the idea

There were 2 groups of 3 trees, and "groups of" means multiply.

Number sentence =2\times 3

Idea summary

If we need to find the total for multiple equal groups, we need to multiply.

## Story problems with multiplication and division

How do we know if we need to multiply or divide, when we have a story problem? Let's see if we can find some clues, in this video.

### Examples

#### Example 2

A teacher wants to divide up her class of 6 students evenly onto 3 tables.

a

Write a number sentence for this story problem.

Worked Solution
Create a strategy

The word "divide" tells us that we should use division.

Apply the idea

The teacher will have to divide the 6 students into 3 equal groups.

Number sentence = 6\div3

b

How many students will there be at each table?

Worked Solution
Create a strategy

To find the number of students at each table we need to solve the number sentence from part (a).

Apply the idea

The picture shows 6 squares split into 3 rows:

There are 2 squares in each row. So: 6\div 3 = 2.

So there will be 2 students at each table.

Idea summary
• If we have a total to share, we use division to work out how many groups, or how many in each group.

• If we have a number of equally sized groups, we need to multiply to work out the total.

• Multiplication and division are opposites but you can use fact families to help you to solve questions.

### Outcomes

#### MA2-6NA

uses mental and informal written strategies for multiplication and division

#### MA2-8NA

generalises properties of odd and even numbers, generates number patterns, and completes simple number sentences by calculating missing values