96
Parallel lines
Textbook: Part 3, lesson 96, pp. 86–88
GoalParallel lines: they never meet and the distance between them is the same everywhere; drawing a parallel line through a given point.
New words
parallel · parallelstraight line · to‘g‘ri chiziqto intersect · kesishmoqdistance · masofa
Explanation
If two straight lines never meet, however far they are extended, they are called parallel. The distance between parallel lines is the same everywhere. Railway tracks, the lines of a notebook and the opposite sides of a rectangle are examples. We write a ∥ b. To draw a line parallel to a given one we use the squares of a notebook, or a ruler and a set square.
Worked examples
Two horizontal lines of a notebook are parallel: the distance between them is the same at the left edge and at the right edge of the page.
In a rectangle ABCD, AB ∥ DC and AD ∥ BC: there are 2 pairs of parallel sides.
Class activity
“Find the parallels”: children look for parallel lines in the classroom (window frame, board, desk edge, floorboards) and sketch the pairs in their notebooks.
Practice
1
How many pairs of parallel sides does a rectangle have?
2
2
Five parallel horizontal lines are drawn for writing music. How many gaps are there between them?
4
3
A horizontal segment AB is 15 cm. Point K is 6 cm to the right of A and point L is 4 cm to the left of B. How many centimetres is the segment KL?
5
4
The distance between two parallel lines is 3 cm. How many centimetres is the distance at their right ends?
3
5
Express 6 m 5 dm 3 cm + 2 m 7 dm in centimetres.
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