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Chapter 13 of 15
Flashcards

Geometrical Constructions

Kerala Board · Class 9 · Mathematics

Flashcards for Geometrical Constructions — Kerala Board Class 9 Mathematics. Quick Q&A cards covering key concepts, definitions, and formulas.

45 questions20 flashcards5 concepts
20 Flashcards
Card 1Basic Constructions

Construct the perpendicular bisector of line segment AB = 6 cm using ruler and compass only. List the steps.

Answer

Step 1: Draw line segment AB = 6 cm. Step 2: Take A as center, draw arc with radius > 3 cm on both sides of AB. Step 3: Take B as center with same radius, draw arcs intersecting previous arcs at P and

Card 2Proof and Justification

Prove that in perpendicular bisector construction, the line PQ actually bisects AB perpendicularly.

Answer

Proof: In triangles PAQ and PBQ: AP = BP (equal radii), AQ = BQ (equal radii), PQ = PQ (common). Therefore △PAQ ≅ △PBQ (SSS rule). So ∠APO = ∠BPO (CPCT). In △APO and △BPO: AP = BP, ∠APO = ∠BPO, OP = O

Card 3Angle Construction

Construct an angle of 60° at point A on ray AB using compass and ruler. Show all steps.

Answer

Step 1: Draw ray AB with initial point A. Step 2: Take A as center with any radius, draw arc intersecting AB at D. Step 3: Take D as center with same radius, draw arc intersecting previous arc at E. S

Card 4Angle Construction

How do you construct a 30° angle using the 60° angle construction?

Answer

Step 1: First construct 60° angle using standard method. Step 2: Bisect the 60° angle. Method: Take any radius from vertex, mark arcs on both rays. From these points, draw equal arcs intersecting insi

Card 5Triangle Construction

Construct triangle ABC with BC = 5 cm, ∠B = 60°, and AB + AC = 8 cm. Show construction steps.

Answer

Step 1: Draw BC = 5 cm. Step 2: At B, construct ∠CBX = 60°. Step 3: From B on ray BX, mark point D such that BD = 8 cm. Step 4: Join CD. Step 5: Draw perpendicular bisector of CD meeting BD at A. Step

Card 6Concept Understanding

Why does the construction AB + AC = BD work in the previous triangle construction?

Answer

Conceptual explanation: When we mark D on BX such that BD = AB + AC, and draw perpendicular bisector of CD, point A lies equidistant from C and D. Therefore AC = AD. Since A lies on BD, we have BD = B

Card 7Triangle Construction

Construct triangle PQR with QR = 6 cm, ∠Q = 45°, and PQ - PR = 2 cm (where PQ > PR).

Answer

Step 1: Draw QR = 6 cm. Step 2: At Q, construct ∠RQX = 45°. Step 3: On QX, mark point S such that QS = 2 cm (= PQ - PR). Step 4: Join RS. Step 5: Draw perpendicular bisector of RS meeting QX at P. Ste

Card 8Problem Strategy

When should you use case (i) vs case (ii) for difference of sides construction?

Answer

Case (i): When AB > AC, use AB - AC. Mark point D on AB extended such that BD = AB - AC. Case (ii): When AB < AC, use AC - AB. Mark point D on AB produced such that BD = AC - AB. Key difference: In ca

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Frequently Asked Questions

What are the important topics in Geometrical Constructions for Kerala Board Class 9 Mathematics?

Geometrical Constructions 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.

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.

There are 20 flashcards for Geometrical Constructions covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.