Triangles — Class 10 MCQs with Answers
Class 10 CBSE Mathematics · Chapter 6
108 practice questions · 31 Easy · 39 Medium · 38 Hard · Updated
Jump to the 6 solved questions
Practise the most important Class 10 CBSE Mathematics questions from Chapter 6, "Triangles". You get 11 timed quizzes made from 108 NCERT-based MCQs, with answers and explanations. The questions are split into 31 Easy, 39 Medium and 38 Hard. Warm up on the basics, then move on to the exam-level questions that top scorers in CBSE Board exams and the JEE & NEET foundation years get right.
To score well in "Triangles", focus on fast problem-solving, formula recall and step-by-step working. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This helps you stay accurate when time is short, just as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Triangles, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 10 Mathematics mastery score. Try the 6 sample questions below: tap an option to see the answer and a worked explanation. Sign in free to start practising.
Triangles — important questions & MCQs with answers (Class 10 Mathematics)
6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.
0 of 6 answered
- Q1 of 6Easy
Two triangles are similar if their corresponding angles are equal and corresponding sides are:
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Answer: Proportional
Explanation: Similar triangles need equal corresponding angles AND proportional corresponding sides — equal sides alone would make them congruent, not just similar.
- Q2 of 6Easy
BPT (Basic Proportionality Theorem) is also known as:
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Answer: Thales Theorem
Explanation: The Basic Proportionality Theorem is called Thales' Theorem after the Greek mathematician who first proved that a line parallel to one side of a triangle divides the other two proportionally.
- Q3 of 6Medium
In ΔABC, DE ∥ BC, AD = 4, DB = 6, AE = 6. Then EC equals:
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Answer: 9
Explanation: By the Basic Proportionality Theorem, DE ∥ BC gives AD/DB = AE/EC, so 4/6 = 6/EC, and cross-multiplying gives EC = 36/4 = 9.
- Q4 of 6Medium
Assertion (A): A square of side 4 cm and a rectangle of sides 4 cm and 6 cm are not similar. Reason (R): All equilateral triangles are similar.
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Answer: Both A and R are true but R is not the correct explanation of A
Explanation: A is true: their angles are equal, but their sides are not in the same ratio (4/4 ≠ 4/6). R is also true, but it is about triangles and does not explain A.
- Q5 of 6Hard
If △ABC ~ △DEF with AB=4, DE=6, area(ABC)=16. area(DEF)=?
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Answer: 36
Explanation: Since ΔABC ~ ΔDEF, area ratio = (AB/DE)² = (4/6)² = 4/9, so area(DEF) = 16 × 9/4 = 36 — using the side ratio 4/6 directly instead of squaring it gives the wrong option.
- Q6 of 6Hard
Assertion (A): In ΔPQR, E is on PQ and F is on PR with PE = 3 cm, EQ = 5 cm, PF = 4.5 cm and FR = 7.5 cm. Then EF ∥ QR. Reason (R): If a line divides any two sides of a triangle in the same ratio, then the line is parallel to the third side.
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Answer: Both A and R are true and R is the correct explanation of A
Explanation: A is true: PE/EQ = 3/5 = 0.6 and PF/FR = 4.5/7.5 = 0.6, so EF divides the two sides in the same ratio. R is the converse of the Basic Proportionality Theorem, and it gives A.
Triangles notes: key concepts (Class 10 Mathematics)
Two triangles are similar when their shapes match even if their sizes do not, and similarity is what makes indirect measurement possible. This chapter builds the Basic Proportionality Theorem, the similarity criteria, the area ratio, and the Pythagoras theorem with its converse.
- Similar triangles
- Triangles whose corresponding angles are equal and whose corresponding sides are in the same ratio — the same shape at possibly different sizes.
- Congruence versus similarity
- Congruent triangles are identical in both shape and size; similar triangles share only shape, so congruence is the special case where the ratio is 1.
- Basic Proportionality Theorem (Thales)
- A line drawn parallel to one side of a triangle divides the other two sides in the same ratio.
- Converse of BPT
- If a line divides two sides of a triangle in the same ratio, then that line must be parallel to the third side.
- AAA / AA similarity criterion
- If two angles of one triangle equal two angles of another, the triangles are similar — the third pair is then automatically equal.
- SSS similarity criterion
- If corresponding sides of two triangles are in the same ratio throughout, the triangles are similar.
- SAS similarity criterion
- If one pair of angles is equal and the sides containing those angles are proportional, the triangles are similar.
- Ratio of areas of similar triangles
- The ratio of the areas equals the SQUARE of the ratio of any pair of corresponding sides.
- Pythagoras theorem
- In a right triangle the square on the hypotenuse equals the sum of the squares on the other two sides.
- Converse of Pythagoras
- If the square of the longest side equals the sum of the squares of the other two, the triangle is right-angled — the standard test for a right angle.
- Similarity in a right triangle's altitude
- The perpendicular from the right angle to the hypotenuse creates two triangles each similar to the original and to each other.
- Pythagorean triplet
- A set of three whole numbers satisfying a² + b² = c², such as 3-4-5 and 5-12-13, which recur constantly in problems.
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Triangles — FAQs
What are the key concepts in Class 10 Mathematics Triangles?+
Two triangles are similar when their shapes match even if their sizes do not, and similarity is what makes indirect measurement possible. This chapter builds the Basic Proportionality Theorem, the similarity criteria, the area ratio, and the Pythagoras theorem with its converse. Key ideas include Similar triangles, Congruence versus similarity, Basic Proportionality Theorem (Thales), Converse of BPT, AAA / AA similarity criterion, SSS similarity criterion.
What does Class 10 Mathematics Chapter 6 (Triangles) cover on XamBaaz?+
It has 108 NCERT-based MCQs on "Triangles": 31 Easy, 39 Medium and 38 Hard. Together they make 11 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE Board exams and the JEE & NEET foundation years.
Are these "Triangles" questions free to practise?+
Yes. Sign in with Google to practise "Triangles" free. Full unlimited access is ₹999/year. One year from the day you pay. You stay in Class 10 till 31 March; on 1 April your account moves up to Class 11 and the rest of your year carries over. No chapter is charged separately.
How should I revise "Triangles" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 11 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Triangles" MCQs available with answers?+
Yes. 6 sample questions are on this page with answers: tap an option, or "Show answer", to see the correct option and a step-by-step explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Triangles" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Triangles (Class 10 Mathematics)?+
The questions that matter most test Similar triangles, Congruence versus similarity, Basic Proportionality Theorem (Thales), Converse of BPT, AAA / AA similarity criterion, SSS similarity criterion. This page shows 6 solved important MCQs with answers and explanations. Sign in to practise all 108 questions on the chapter as timed quizzes.
Is there an online quiz for Triangles?+
Yes — Class 10 Mathematics Triangles has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.
Are there question answers and extra questions for Triangles (Class 10 Mathematics)?+
Yes. This page has 6 solved questions on Triangles, each with the correct answer and a short explanation. Sign in to practise all 108 questions on the chapter as timed quizzes.
Are there assertion–reason and case study questions for Triangles (Class 10 Mathematics)?+
Yes. The Triangles question bank has 6 assertion–reason questions and 12 case-based (case study) questions in the CBSE board format, alongside the regular MCQs. Each comes with the answer and a worked explanation. Sign in to practise them in timed quizzes.