Lines, triangles & quadrilaterals
Parallel lines, triangle angles, congruence and parallelograms.
Learn with Kutty
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When a line cuts across two parallel lines, the angles repeat.
Look: The same pattern of angles at both crossings: 60° and 120°.
✏️ Your turn!
Type your answer and press Check. Kutty will tell you if it is right.
1One angle on a line is 75°. The other?
2Same-position angle to a 50° angle?
3Angles in a triangle add to?
! Careful!
✗Using these rules when lines are not parallel.
✓They only work for parallel lines.
✗Thinking side-by-side angles are equal.
✓Side by side on a line, they add to 180°.
See the whole lesson on one page
When a line cuts across two parallel lines, the angles repeat.
Angles in the same position at each crossing are equal. Angles in a Z shape are equal. Angles side by side on a line add to 180°.
Think of it like thisRailway tracks are parallel. A road crossing them makes the same angle at each rail.
- Parallel
- Lines that never meet, like rails.
Solved together
In a Z shape between parallel lines, one angle is (3x + 10)° and the other is (5x − 30)°. Find x.
Z-angles are equal.
3x + 10 = 5x − 30Solve.
40 = 2xx = 20Check: 3(20) + 10 = 70 and 5(20) − 30 = 70. ✓
Answerx = 20; both angles are 70°.
Now practise it
Kanakku makes new questions on lines, triangles & quadrilaterals every time. It shows the working and gives a hint when you are stuck.