Garden BedsTask 147 ... Years 4  10SummaryPlants are sown in a row and a path of tiles is built to enclose them. If you are told any number of plants, can you calculate the number of tiles needed. But this is only the start of an investigation which can illustrate most of the elements of pattern and algebra. Trying different numbers of tiles to check the hypothesised rule is substituting into and equation. Asking the backwards question, If I tell you the number of tiles, can you tell me the number of plants? is solving an equation. Application of the mathematician's question, Can I check it another way?, leads to equivalent algebraic expressions. Realising that plants and tiles form number pairs with an order  the number of plants determines the number of tiles  leads to linear graphs.This cameo has a From The Classroom section which shows that the problem is a meaningful investigation for Year 2 children, who get quite excited about the numbers they are challenged to work with and the patterns they find. Garden Beds also appears on the Picture Puzzles Pattern & Algebra B menu where the problem is presented using one screen, two learners, concrete materials and a challenge. 
Materials
Content

IcebergA task is the tip of a learning iceberg. There is always more to a task than is recorded on the card. 
In true textbook style the card first asks students to work out the number of tiles for 1, 2, 5 and 10 tiles. The first three can be found using the tiles if necessary, but the fourth encourages further visualisation, either with a sketch or imagined. The answers are: 8, 10, 16 & 26. However, correct answers does not reveal the method for working them out. Perhaps the students 'see' a construction pattern such as 2 tiles for each plant and 3 more for each end. But perhaps they have used a form of tabulation and discovered a number pattern such as this...
Question 2 encourages students to explain and either of the approaches above will lead to a generalisation that will provide the answer for 100 plants (206 tiles).
ExtensionsThe challenge opens the door to equivalent algebraic expressions and several other extensions are suggested in the summary above. There are also the What happens if..? questions such as:

Whole Class InvestigationTasks are an invitation for two students to work like a mathematician. Tasks can also be modified to become whole class investigations which model how a mathematician works. 
Garden Beds can be introduced away from the front of the room on the floor or sufficiently large table using squares of card or coloured paper similar to the tiles in the task. You will also need sets of tiles or blocks for each pair. Present the story shell and involve students in placing the cards. Record data from various lengths of garden bed on the white board and set the main challenge of If I tell you any number of plants can you tell me the number of tiles?. Invite students to return to their tables with a partner to explore this question with the tiles. Poly Plug can also be used if you adjust the story to be stepping stones bordering the garden beds in the same way. Develop the lesson into pattern, tables, equivalent algebraic expressions, backwards questions, ordered pairs or graphing as appropriate. There is sufficient in this investigation to spend several lessons with it For more ideas and discussion about this investigation, open a new browser tab (or page) and visit Maths300 Lesson 16, Garden Beds, which also includes software and an investigation guide with answers and discussion. You will also find some fantastic student work in the Classroom Contributions, including some amazing PowerPoint presentations from students at Settlebeck High School, UK. Visit Garden Beds on Poly Plug & Tasks. 
Is it in Maths With Attitude?Maths With Attitude is a set of handson learning kits available from Years 310 which structure the use of tasks and whole class investigations into a week by week planner. 
The Garden Beds task is an integral part of:
The Garden Beds lesson is an integral part of:

Svartedalsskolan
Jakob Norrby 
Jakob's school organised a half day Discussion Lesson program with a visitor from Mathematics Centre. Jakob observed a Year 9 class exploring Garden Beds. He was thrilled with the way the learning unfolded with these teenagers. As the teachers' discussion after the lesson unpacked the teaching craft, Jakob decided that his Year 2 children could understand the problem and learn from it. After lunch he invited the visitor to observe these much younger children at work on the problem and both were excited by the children's enthusiasm for the problem and willingness to extend it to 'big numbers'. 
Telling the Story My Grampa planted a garden with three plants.
They went all the way around. 
Extending the Story
Grampa liked his plants so much that the next year he planted 5. 
Will you help me make the path so we can check your guesses? Great so if there are five plants he will need 16 stones. 
The next phase of the lesson encouraged exploring different size gardens  first 6 plants ... then 10 ... then 20. Lots of work with materials and lots of recording. Some children gave up modelling and began drawing, especially when the number of plants got bigger.
Can you see the children's concentration and enthusiasm for the problem and pride in their work? Some began to sense that because of the building pattern, they didn't have to count all the way around to know the answer. 