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.Operative techniques by decomposing figures in order to calculate more easily the perimeter or the area of a figure or to compare the perimeter and the area of two figures in geometry in the sixth grade. We will end this chapter with the calculation of duration and the conversion of time, but we will also see how to add or subtract to calculate the duration between two events.
I. Lengths and perimeters
1. concept of perimeter
Example: perimeter of a polygon.
To calculate the perimeter P of this polygon, we add the lengths of each side.
.
The perimeter of this polygon is 7.9 cm.
2. perimeter of a rectangle and a square
Example:
The perimeter P of the rectangle shown below is :
The perimeter of the rectangle is 8 cm.
3. perimeter of a circle
.
Example:
The perimeter of a circle of radius 3 cm is
II.Areas
1. figure areas
Example:
The area of the figure below is equal to six units.
2.area units
Other area units
The square decimeter (dm²) is the area of a square of side 1 dm.
A square of area 1 m² contains 100 squares of area 1 dm².
So .
To measure the area of land, the are (a) and the hectare (ha) are used: and .
3.areas of particular polygons
4. area of a disk
III. durations
1.Duration
The measure of time between two moments is called duration. A unit of time often used is the second (s).
Other units of duration:
Example:
A movie starts at 5:40 pm and ends at 7:10 pm.
Its duration is 20 min + 1 h 10 min=1 h 30 min.
This session lasted 1 h 30 min.
Did you learn about perimeters and areas in 6th grade?
Un QCM de maths sur les périmètres et aires de figures. en 6ème.
Skills to learn about perimeters and areas:
- Know the definition of the perimeter and area of a figure;
- Know the formulas for the square, the rectangle, the circle;
- Know how to convert lengths;
- Know how to convert areas;
- Solve problems.
This course is in accordance with the official programs of thenational education.
As a complement, you can consult the exercises on the perimeter and area of a figure in sixth grade.
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