Class 9 Maths Chapter 7 (Triangles) MCQs are provided here with answers, online. Students can practice these objective questions to score good marks in the final exam (2020-2021). All the problems here are based on the CBSE syllabus and NCERT curriculum. A detailed explanation is given for each question to help students understand the concepts. Learn chapter-wise MCQs, only at BYJUâ€™S. Also, check Important Questions for Class 9 Maths.

## MCQs on Class 9 Triangles

Solve the MCQs given below and choose the correct answer among the four options. Match your answers with the given answers here.

**1) In triangle ABC, if AB=BC and âˆ B = 70Â°, âˆ A will be:**

a. 70Â°

b. 110Â°

c. 55Â°

d. 130Â°

Answer:** c**

Explanation: Given,

AB = BC

Hence, âˆ A=âˆ C

And âˆ B = 70Â°

By angle sum property of triangle we know:

âˆ A+âˆ B+âˆ C = 180Â°

2âˆ A+âˆ B=180Â°

2âˆ A = 180-âˆ B = 180-70 = 110Â°

âˆ A = 55Â°

**2) For two triangles, if two angles and the included side of one triangle are equal to two angles and the included side of another triangle. Then the congruency rule is:**

a. SSS

b. ASA

c. SAS

d. None of the above

Answer:** b**

**3) A triangle in which two sides are equal is called:**

a. Scalene triangle

b. Equilateral triangle

c. Isosceles triangle

d. None of the above

Answer:** c**

**4) The angles opposite to equal sides of a triangle are:**

a. Equal

b. Unequal

c. supplementary angles

d. Complementary angles

Answer:** a**

**5) If E and F are the midpoints of equal sides AB and AC of a triangle ABC. Then:**

a. BF=AC

b. BF=AF

c. CE=AB

d. BF = CE

Answer:** d**

Explanation: AB and AC are equal sides.

AB = AC (Given)

âˆ A = âˆ A (Common angle)

AE = AF (Halves of equal sides)

âˆ† ABF â‰… âˆ† ACE (By SAS rule)

Hence, BF = CE (CPCT)

**6) ABC is an isosceles triangle in which altitudes BE and CF are drawn to equal sides AC and AB respectively. Then:**

a. BE>CF

b. BE<CF

c. BE=CF

d. None of the above

Answer:** c**

Explanation:

âˆ A = âˆ A (common arm)

âˆ AEB = âˆ AFC (Right angles)

AB = AC (Given)

âˆ´ Î”AEB â‰… Î”AFC

Hence, BE = CF (by CPCT)

**7) If ABC and DBC are two isosceles triangles on the same base BC. Then:**

a. âˆ ABD = âˆ ACD

b. âˆ ABD > âˆ ACD

c. âˆ ABD < âˆ ACD

d. None of the above

Answer:** a**

Explanation: AD = AD (Common arm)

AB = AC (Sides of isosceles triangle)

BD = CD (Sides of isosceles triangle)

So, Î”ABD â‰… Î”ACD.

âˆ´ âˆ ABD = âˆ ACD (By CPCT)

**8) If ABC is an equilateral triangle, then each angle equals to:**

a. 90Â°

B.180Â°

c. 120Â°

d. 60Â°

Answer:** d**

Explanation: Equilateral triangle has all its sides equal and each angle measures 60Â°.

AB= BC = AC (All sides are equal)

Hence, âˆ A = âˆ B = âˆ C (Opposite angles of equal sides)

Also, we know that,

âˆ A + âˆ B + âˆ C = 180Â°

â‡’ 3âˆ A = 180Â°

â‡’ âˆ A = 60Â°

âˆ´ âˆ A = âˆ B = âˆ C = 60Â°

**9) If AD is an altitude of an isosceles triangle ABC in which AB = AC. Then:**

a. BD=CD

b. BD>CD

c. BD<CD

d. None of the above

Answer:** a**

Explanation: In Î”ABD and Î”ACD,

âˆ ADB = âˆ ADC = 90Â°

AB = AC (Given)

AD = AD (Common)

âˆ´ Î”ABD â‰… Î”ACD (By RHS congruence condition)

BD = CD (By CPCT)

**10) In a right triangle, the longest side is:**

a. Perpendicular

b. Hypotenuse

c. Base

d. None of the above

Answer:** b**

Explanation: In triangle ABC, right-angled at B.

âˆ B = 90

By angle sum property, we know:

âˆ A + âˆ B + âˆ C = 180

Hence, âˆ A + âˆ C = 90

So, âˆ B is the largest angle.

Therefore, the side (hypotenuse) opposite to largest angle will be longest one.

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