Belinda is looking at the site plans. She has to work out the layout of the houses being built on the site and the positioning of the house plots using her knowledge of calculating perimeter.
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Discussion points for teachers
1. Do you agree?
Discuss calculating the perimeter of the house using the given dimensions.
No, the perimeter is 46m.
2. Work out the perimeter of the gardens.
Discuss working out the outer dimensions of the rectangle with a 80m perimeter, to then work out the dimensions of each edge, to then calculate the perimeters.
20m + 20m + 14m + 12m + 8m + 6m = 80m (large part of garden); 1m + 1m + 1m + 1m = 4m (small garden plot) = total 84m
3. Use the plan of the site to work out the possible dimensions of the site.
Discuss breaking up the total perimeter between four sides first and then compensating with the different parts that intrude or protrude from the basis rectangle. This question is open-ended for the children to explore.
Various answers, for example: Starting at the top left of the plan and working clockwise around, the dimensions are: 50m + 50m + 100m + 50m + 50m + 50m + 50m + 100m + 80m + 50m + 50m + 50m + 120m + 150m
4. Help her to complete the chart.
Discuss the dimensions on the drawings to work out the missing perimeters.
5. What could the previous plan have looked like?
Discuss using the perimeter given to determine which four numbers would equal the total needed.
Various answers, for example: 19m + 19m + 4m + 4m = 46m
6. The layout is not as it should be, but which house and which garden have they combined by mistake?
Discuss using previously worked out measurements to see which house and garden has been combined.
House type C and the perimeter of garden type B.
7. What could the dimensions of the two separate areas be?
Discuss working out the outer dimensions to give a perimeter of 54m, to then be able to allocate measurements to the inside shape. This question is open-ended for the children to explore.
Various answers, for example: Playground dimensions = 8m by 11m; Grassed area = 15m by 12m
National Curriculum Objectives:
Mathematics Year 4: (4M7a) Measure and calculate the perimeter of a rectilinear figure (including squares) in centimetres and metres
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