In this lesson plan, students are given the task of compiling a book order for $75. They are required to use addition and  subtraction strategies to problem solve the best solution.

• Represent money values in multiple ways and count the change required for simple transactions to the nearest five cents (ACMNA059)
• Recognise and explain the connection between addition and subtraction (ACMNA054)

Year 4 Mathematics:

• Apply place value to partition, rearrange and regroup numbers to at least tens of thousands to assist calculations and solve problems (ACMNA073)
• Investigate number sequences involving multiples of 3, 4, 6, 7, 8, and 9 (ACMNA074)
• Solve problems involving purchases and the calculation of change to the nearest five cents with and without digital technologies (ACMNA080)

Students are able to use a range of strategies for addition and subtraction involving two-digit numbers including counting on, jump, split and combining numbers and also have an understanding that addition and subtraction are inverse equations. They recognise that the number system is a base ten number system and have an understanding of the place value of ones and tens. Students also have a basic understanding of the role of the decimal point in the place value system ie. 10.00 is the same as 10 and recognise that amounts of money are written with two decimal places. They are also able to use the symbol ‘$’ to express dollars.

This experience will provide students with an authentic and meaningful context to practice their mathematical skills of addition and subtraction in number. The use of an authentic artefact (catalogue) supports students in knowing how to apply mathematical understandings in real life contexts. Further, providing an open-ended problem solving experience will support students to develop and use their own strategies and promote higher order levels of thinking. Lastly engaging the interests of students and the promise of books being purchased for the classroom will provide a highly motivating experience.

For students to:

• Use mental and/or written strategies to add and subtract whole numbers and basic decimal number;
• Chose their most effective strategy to solve the problem
• Find the best selection of books for $75 and be able to justify and explain their decisions

Lesson:

Students are given the task of compiling a proposal for a book order for the classroom library. They are provided with the guidelines including a budget of $75 and instructions to find the best selection of books for the best price. Students are reminded to consider what books are already in the classroom and to ensure a variety of books are purchased that suit the different interests and reading levels within the group. Students access the Scholastic online catalogue to research their order.

Students can choose what written and mental computation strategies they employ to ensure the order is within budget. They record the strategies they have used and check their own answers. Where required, students may be encouraged to use grid paper to assist in placing numerals in correct columns for written algorithms. Students compile their book order form including a small persuasive statement to justify the reasoning behind their selection of books.

Student swap proposals for peer review checking and feedback, and for an opportunity to justify to their peers their selections and share their strategies for working out the problem Students submit their book orders and the top three orders are chosen before the class votes for the favourite order of books.

Questioning to Extend Working Mathematically Focus:

• What strategy did you use to calculate your findings? Is there another way you could do this? (Problem solving)
• How can you check that your solution is correct? Is there another way you could check? (Reasoning)
• How can you write out the problem? Is there another way you could represent the problem? (Problem solving)
• Why did you select these books, tell me about your reasoning. (Reasoning)
• How much change would you get back if you paid $75? (Problem solving)

Integration of Technology:

The internet access to the online catalogue provides an opportunity for students to engage with a real artefact and provides an interactive stimulus to motivate students. Calculators are an option for students to check their own strategies should this be needed.

Assessment:

Through questioning techniques of strategies and student’s reasoning; observing conversations between peers during peer feedback; through viewing work sample – written strategies, book order and justification statement.

Resources:

• Book Order Proposal Form (PDF)
• Computers and Internet to access Scholastic Catalogue http://www.scholastic.com.au/schools/bookclub/arrow.asp (External link)
• Pencils, paper and grid paper;
• Calculators if required.

 

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