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Unit review
Textbook: Part 3, pp. 127–128
GoalReview: parallel and perpendicular lines, the number ray, the coordinate grid, equations, symmetry.
New words
parallel · parallelcoordinate · koordinataequation · tenglamaaxis of symmetry · simmetriya o‘qi
Explanation
Let us review. Parallel lines never meet; perpendicular lines meet at a right angle. On a number ray the coordinate of a point is its distance from zero; the point with the smaller coordinate lies further left. On the coordinate grid a point is written (x; y): first steps along OX, then along OY. In an equation we undo the last operation with its inverse, calculate numerical expressions first and check the root. A symmetrical shape folded along the axis has halves that coincide.
Worked examples
A rectangle with sides 40 mm and 25 mm: opposite sides are parallel, adjacent sides perpendicular. Perimeter 2 × (40 + 25) = 130 mm, area 40 × 25 = 1 000 mm².
6 × x + 18 000 = 48 000 → 6 × x = 30 000 → x = 5 000 (sum).
Class activity
“Review trail”: five stations in the classroom: lines, number ray, coordinate grid, equation, symmetry. Teams do one task at each station and earn a stamp.
Practice
1
A rectangle has sides 40 mm and 25 mm. What is its perimeter in millimetres?
130
2
A rectangle has sides 40 mm and 25 mm. What is its area in square millimetres?
1000
3
On a ray the value of a division is 8. Which number is at the 5th mark to the right of zero?
40
4
Which point lies further left: A(500 071) or B(500 017)?
B
5
Solve f × 60 = 9 000 − 5 400.
60
6
An album costs x sum. Dad bought 6 albums and a paint set for 18 000 sum and paid 48 000 sum in all. How many sum is one album?
5000
7
The letters A, T, H have 1, 1 and 2 axes of symmetry. How many axes in all?
4