# 6.06 Purchases and change

Lesson

## Ideas

We need to remember how to  calculate the total  amount of money that we have. Let's try this problem.

### Examples

#### Example 1

Which of the following shows a total of \$22.50? A B Worked Solution Create a strategy Add the value of each note and coin using the vertical algorithm. Use this table of values to help you. Apply the idea For Option A, write the addition of values in a vertical algorithm and add the digits in each column. \begin{array}{c} & &2&0&.&0&0 \\ & &&2&.&0&0 \\ &+&&0&.&5&0 \\ \hline & &2&2 &. &5&0 \\ \hline \end{array} The total amount of notes and coins in Option A is \$22.50.

For Option B, write the addition of values in a vertical algorithm and add the digits in each column.

\begin{array}{c} & &2&0&.&0&0 \\ & &&5&.&0&0 \\ &&&1&.&0&0 \\ &+&&1&.&0&0 \\ \hline & &2&7 &. &0&0 \\ \hline \end{array}

The total amount of notes and coins in Option B is \$27.00. So the correct answer is option A. Idea summary The value of a coin is written on the coin. Silver coins are for cents, and gold coins are for dollars. All notes have dollar values. The value is written on the note. To add money we can write the values as decimals and add them using a vertical algorithm. ## Money and change Let's learn more about calculating change. Loading video... ### Examples #### Example 2 How much change would you receive from \$10 if you spent \\$7.50?

Worked Solution
Create a strategy

Use a number line and count back from 10 by 7.50.

Apply the idea

Plot 10 on the number line:

Count back by 7 to get to 3:

Count back by 0.5 to get to 2.5:

Idea summary

We can either count up or count back to find the difference between the amount of money we start with and the amount of money that we spent.

### Outcomes

#### MA2-5NA

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers