perimeter and area of a victim lesson
Area and Perimeter are common mathematical calculations. Often thought of, and used in similar circumstances though their formulas are very different. Both calculations are used to define aspects of two dimensional shapes or spaces, such as squares, triangles, rectangles, or circles.
The perimeter of any two dimensional object is the total distance around the OUTSIDE of an object, measured in specific units. Perimeter is measured by adding the lengths of every side of a shape or object. Klerk, J (2007) p. 97.
The easiest way to calculate a complex shape is to break the 2D shape down into parts that are more easily measured.
INTRODUCTION
The goals for this activity include a review of your current knowledge of how to measure the perimeter and area of complex 2 dimensional shape: in this case the chalk outline of a fellow student.
This activity will be monitored with short achievable goals set by your teacher so that you can illustrate your mathematical competencies.
The perimeter of any two dimensional object is the total distance around the OUTSIDE of an object, measured in specific units. Perimeter is measured by adding the lengths of every side of a shape or object. Klerk, J (2007) p. 97.
The easiest way to calculate a complex shape is to break the 2D shape down into parts that are more easily measured.
INTRODUCTION
The goals for this activity include a review of your current knowledge of how to measure the perimeter and area of complex 2 dimensional shape: in this case the chalk outline of a fellow student.
This activity will be monitored with short achievable goals set by your teacher so that you can illustrate your mathematical competencies.
PERIMETER ACTIVITY
In pairs you will be asked to use string to measure the perimeter of a chalk drawn body outline on concrete. You will then be asked to estimate the overall length of the perimeter of the outline before actually measuring it using a long length of string.
Ask the rest of the class what their perimeter lengths were to compare the differences. The class should go around and look at the body shapes, methods of calculation and results for discussion.
- One student lies down on the concrete and the other uses chalk to trace around their shape.
- Estimate how big you think the perimeter is of the shape and record that estimate on the concrete next to the body shape.
- Cut and then use your estimated length of string to measure all the lengths around the body. Tape the end of each length down to the concrete. Keep doing this all the way around the body.
- If your estimated length is too short, estimate how much more you think you will need and cut that length to add to the process. Record the extra length you added to your original estimate.
- Once you get all the way around the body, cut the string.
- Lay the string out straight, on the pavement, write out the addition of ALL the lengths to gain your answer before actually measuring the entire length of the string with the tape measure. Compare the estimate, to the sum of all lengths.
- Measure the overall length with the tape measure to get the perimeter and discuss the findings.
- Finally, measure the overall length of the string to test the difference in the estimate, sum of all sides, to the overall length.
Ask the rest of the class what their perimeter lengths were to compare the differences. The class should go around and look at the body shapes, methods of calculation and results for discussion.
AREA ACTIVITY
- Estimate what you think the area of the body shape will be and write your estimate/prediction on the concrete.
- Use a bright coloured chalk to rule a square grid over the shape from top to bottom (see photos). Use a fence paling to rule the grid or a meter ruler.
- You could use one colour for the full units of measure and another colour to calculate the ½ units.
- Work with your partner. Colour in all the full square first e.g. in green. One person should colour in the squares and the other should keep a tally on the concrete so you can visually check your work if you loose track.
- You should now be able to clearly see all the full squares.
- Now take a different coloured chalk to CAREFULLY make decisions about the fractions/partial parts of the body shape. Add up the 1/2s, 1/4s etc ... . Decisions about how to make up a
whole unit when it comes to 1/2, 1/3 and 1/4 make this an interesting
collaborative activity.
- This is part of the activity really requires you to work together, recording, decision making and documenting. Accurate recording is crucial.
- Keep the tally in the same colour for clarity of work e.g. purple.
- Add up the tally and discuss your findings.
If you can leave all the work for the rest of the school to see, do. Write this question next to all of the work. Leave a piece of chalk for answers to the question? This is a nice way to celebrate your learning with the rest of the school.