Lines and Angles
Kerala Board · Class 9 · Mathematics
Flashcards for Lines and Angles — Kerala Board Class 9 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.
Find the complementary angle of 35°
Answer
Step 1: Recall that complementary angles sum to 90° Step 2: Let the complementary angle be x Step 3: Set up equation: 35° + x = 90° Step 4: Solve: x = 90° - 35° = 55° Answer: 55°
Two supplementary angles are in the ratio 3:7. Find both angles.
Answer
Step 1: Let the angles be 3x and 7x Step 2: Since supplementary angles sum to 180°: 3x + 7x = 180° Step 3: Combine: 10x = 180° Step 4: Solve: x = 18° Step 5: Find angles: 3x = 3(18°) = 54°, 7x = 7(18°
In intersecting lines, if one angle is 65°, find all four angles formed.
Answer
Step 1: Vertically opposite angles are equal Step 2: Given angle = 65° Step 3: Vertically opposite angle = 65° Step 4: Adjacent angles are supplementary (sum = 180°) Step 5: Other two angles = 180° -
If two parallel lines are cut by a transversal and one angle is 110°, find the corresponding angle.
Answer
Step 1: Recall corresponding angles axiom Step 2: When parallel lines are cut by a transversal, corresponding angles are equal Step 3: Given angle = 110° Step 4: Corresponding angle = 110° Answer: 110
Two parallel lines cut by transversal form alternate interior angles of (3x + 15)° and (2x + 40)°. Find x.
Answer
Step 1: Alternate interior angles are equal when lines are parallel Step 2: Set up equation: 3x + 15 = 2x + 40 Step 3: Subtract 2x from both sides: x + 15 = 40 Step 4: Subtract 15 from both sides: x =
Find the sum of angles in triangle ABC where ∠A = 60° and ∠B = 45°
Answer
Step 1: Use angle sum property: ∠A + ∠B + ∠C = 180° Step 2: Substitute known values: 60° + 45° + ∠C = 180° Step 3: Simplify: 105° + ∠C = 180° Step 4: Solve for ∠C: ∠C = 180° - 105° = 75° Step 5: Verif
In triangle PQR, angles are in ratio 2:3:4. Find all three angles.
Answer
Step 1: Let angles be 2x, 3x, and 4x Step 2: Use angle sum property: 2x + 3x + 4x = 180° Step 3: Combine: 9x = 180° Step 4: Solve: x = 20° Step 5: Find angles: 2x = 40°, 3x = 60°, 4x = 80° Step 6: Ver
Find the exterior angle of a triangle if two interior opposite angles are 35° and 48°
Answer
Step 1: Use exterior angle theorem Step 2: Exterior angle = Sum of two interior opposite angles Step 3: Exterior angle = 35° + 48° Step 4: Exterior angle = 83° Step 5: Verify: Third interior angle = 1
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Lines and Angles covers several key topics that are frequently asked in Kerala Board Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
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Start by understanding all key concepts. Practise previous year questions from this chapter. Revise formulas and definitions regularly. Use flashcards for quick revision before the exam.
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There are 20 flashcards for Lines and Angles covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.
Sources & Official References
- Kerala Board of Public Examinations — keralapareekshabhavan.in
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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