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Triangles — Practice Quiz

ICSE · Class 9 · Mathematics

Try a 4-question quiz on Triangles for ICSE Class 9 Mathematics: tap an answer to check it and see why. 40 questions in the full chapter test.

40 questions30 flashcards5 formulas & key relations5 concepts

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A labeled diagram showing the vertices, sides, and angles of a basic triangle ABC.
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Quick Quiz: Triangles

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Tap an answer to check it instantly. No sign-up needed for these 4.

1

Two triangles ABC and DEF have AB = DE = 6 cm, BC = EF = 4 cm, and ∠B = ∠E = 60°. By which congruence criterion are they congruent?

2

In a triangle, the sum of any two sides must be:

3

If in triangle PQR, ∠P = 70° and ∠Q = 50°, find ∠R:

4

In an isosceles triangle ABC with AB = AC, if ∠A = 40°, find ∠B:

40 Questions·
multiple choicemultiple correct

Sample Questions

1multiple correct

Which of the following are valid congruence criteria for triangles? (Select all that apply)

Show answer

SSS, SAS, ASA, RHS

Valid congruence criteria are: SSS (Side-Side-Side), SAS (Side-Angle-Side), ASA (Angle-Side-Angle), AAS (Angle-Angle-Side), and RHS (Right angle-Hypotenuse-Side). AAA only ensures similarity, not congruence. SSA is not a valid criterion as it can lead to ambiguous cases.

2multiple choice

The exterior angle of a triangle is 120°. If one of the interior opposite angles is 50°, find the other interior opposite angle:

Show answer

70°

By the exterior angle theorem, an exterior angle equals the sum of the two non-adjacent interior angles. So: Exterior angle = Sum of two opposite interior angles. 120° = 50° + other angle. Therefore, other angle = 120° - 50° = 70°.

3multiple correct

If triangle ABC ≅ triangle PQR, and AB = 5 cm, BC = 7 cm, which of the following must be true?

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PQ = 5 cm, QR = 7 cm, ∠A = ∠P, Area of ABC = Area of PQR

When triangles are congruent (ABC ≅ PQR), corresponding parts are equal: AB = PQ = 5 cm, BC = QR = 7 cm, ∠A = ∠P, ∠B = ∠Q (not ∠R), ∠C = ∠R. Congruent triangles have equal areas.

4multiple choice

A triangle can have at most how many obtuse angles?

Show answer

1

A triangle can have at most one obtuse angle. If a triangle had two obtuse angles, their sum would exceed 180° (since each obtuse angle > 90°), but the sum of all three angles in a triangle must be exactly 180°. Therefore, maximum one obtuse angle is possible.

+36 more questions on Triangles (ICSE Class 9 Mathematics)

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Frequently Asked Questions

What are the important topics in Triangles for ICSE Class 9 Mathematics?
Key topics in Triangles include Basic Ideas and Side-Angle Relations, Medians, Centroid, Altitudes and Orthocentre, Angle Sum, Exterior Angles and Corollaries, Congruent Triangles and CPCTC. Study these first, then practise questions on each for Class 9 exams.
How many practice questions are there for Triangles?
There are 40 questions on Triangles. Try the 4-question sample quiz on this page first; each answer shows an explanation when you tap it.

Sources & Official References

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

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