GoalReview polygons, quadrilaterals, perimeter, area and liquid volume.
New words
quadrilateral · a flat shape with 4 straight sidesperimeter · the distance all the way round a shapearea · the number of square units inside a shapelitre (L) · a unit of liquid volume; 1 L is 1,000 mL
Explanation
A polygon is a closed flat shape with straight sides. A quadrilateral has 4 sides: the square, the rectangle, the rhombus and the trapezium are all quadrilaterals. The perimeter is the distance around a shape, so we add all the sides. The area is the space inside, so for a rectangle we multiply the length by the width and write square units. A pen 6 m long and 4 m wide has a perimeter of 6 + 4 + 6 + 4 = 20 m and an area of 6 × 4 = 24 square metres. For liquids we use millilitres (mL) for small amounts and litres (L) for large amounts, and 1 L = 1,000 mL.
Worked examples
A garden is 7 m long and 5 m wide. Perimeter: 7 + 5 + 7 + 5 = 24 m. Area: 7 × 5 = 35 square metres.
This trapezium has sides of 10 cm, 5 cm, 4 cm and 5 cm. Its perimeter is 10 + 5 + 4 + 5 = 24 cm. The top and bottom sides are parallel.
Karim has a 2 L bottle of juice and fills glasses of 250 mL. 2 L = 2,000 mL, and 4 glasses fill 1 L, so he fills 2 × 4 = 8 glasses. Check: 8 × 250 = 2,000 mL.
Class activity
Measure a room. Measure the length and width of a rectangular table or mat at home in cm. Find its perimeter and its area. Then fill a 1 L bottle with water, pour it into small cups and count how many cups you fill. Write the size of one cup in mL.
Practice
1
Which shape has 4 equal sides and no square corners?
A, the rhombus.
2
Find the perimeter and the area of this square courtyard.
