## Problem solving with money

Linked from: Number and Algebra: Money and financial mathematics 115-124

### Prerequisites

• Subtraction strategies (Concept builder)
• Understanding money amounts (Concept builder)
• Addition of small amounts of money (Concept builder)
• Change from $1 and$2 (Concept builder)
• Change from larger amounts (Concept builder)

### Key concepts and skills

• Interpreting the presented scenario to find the correct mathematical procedure and operation
• Expressing change in dollars and cents

• Not correctly identifying that 100 cents makes $1 • Misunderstanding that change is the amount left after paying • Arithmetic errors • Misunderstanding of what the question is asking, due to the multi-step nature ### Concept builders Finding change • Provide students with a small collection of coins; for example, 20c, 20c, 50c and 5c. Ask students to find the total value of the coins and then the change from$2.
• Have students complete the process and record their working as they wish.
• As a group, ask students to share their strategies with the group to find the value of the change.
• Repeat with a different set of coins.
• To extend the activity, have items that students need to find the total value of and the relevant change. Students could use a calculator for amounts of cents that cannot be modelled with coins, such as 26 cents.

Solving problems

• Provide students with a problem, such as 'I bought 5 apples that cost 25c each. How much change did I get from $2?' • Have students model the activity, with fruit, price labels and coins. • Have students complete the transaction with money and then with recording. For example, 5 lots of 25 cents is$1.25. $2.00 –$1.25 = 75c. 75c is the amount of change.

• Repeat with a number of examples, working initially with amounts ending in 10 cents and then moving to those ending with 5 cents, keeping below $2. • Strategies such as underlining or recording key information in the question could also be visited. • To vary the activity, extend to include values to the cent, e.g.$1.14, and finding change from values such as $10 and$20. Students should be taught to round values to the nearest 5 cents.