Parallel lines, quadrilaterals and triangles · Usually met around P3
Parallelograms and trapeziums
Two parallel pairs: parallelogram; one pair: trapezium.
How to do it
Method
Two parallel pairs: parallelogram; one pair: trapezium
Rectangles and squares are parallelograms
Another way
Count squares
Both opposite sides go 4 across → parallel
In full
A parallelogram has two pairs of parallel opposite sides, and its opposite sides are equal. Rectangles and squares have two pairs of parallel sides too, so they are parallelograms — special ones with four right angles. A trapezium has only one pair of parallel sides: those two are its bases, usually of different lengths, and the other two are its legs. On dot paper, count how far each side goes across and down: opposite sides with the same moves are parallel. Two parallel pairs make a parallelogram; one pair, a trapezium. To finish a parallelogram from three corners, make the move of one side again from the third corner.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Two neighbouring sides of a parallelogram are 9 cm and 13 cm. How long is the side opposite the 9 cm side?
Show the answer and working
Answer: 9 cm
A parallelogram's opposite sides are equal: 9 cm.
Example 2
How many pairs of opposite sides of the quadrilateral on the dot paper are parallel?
Show the answer and working
Answer: 0 pairs
Opposite sides are parallel when their moves match: 0 pair(s).
Example 3
The shape in the picture is a parallelogram.
True or false?
Show the answer and working
Answer: True
Any quadrilateral with two pairs of parallel sides is a parallelogram — squares and rectangles too.
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