# Fair exchange

Achievement Objectives
NA1-3: Know groupings with five, within ten, and with ten.
Student Activity

She exchanged it with her brother Sam for three coins.

What were the three coins?

Specific Learning Outcomes
Identify the value of coins and notes to \$5.
Devise and use problem solving strategies to explore situations mathematically
Description of Mathematics

This problem shows a knowledge of both coins and what three whole numbers add to 5. It can also be solved using play money.

Required Resource Materials
Activity

### The Problem

Emma had a \$5 note. She exchanged it with her brother Sam for three coins. What were the three coins?

### Teaching Sequence

1. Play "guess the coin" giving clues on its size, its picture, colour etc.
2. Pose the problem to the class.
3. As the students work, either individually or with a partner, ask them questions that focus their thinking on the coins.
Which coin has the largest value?
What could you buy with this coin?
Can you tell me what is on the other side of this coin?
4. Share solutions.

#### Extension to the problem

Emma exchanged the \$5 note for 5 coins. What could they be?

### Solution

The three coins are two \$2 coins and a \$1 coin.

#### Solution to the Extension:

(five \$1) (\$2, \$1, \$1, 50c, 50c)

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