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All questions of Congruence and Similarity for Grade 8 Exam

In ΔABC and ΔPBC, AB = BP and AC = PC. Can you say whether the triangles are congruent to each other or not:
  • a)
    Yes, by ASA Congruence theorem they are congruent
  • b)
    Yes, by SAS Congruence theorem they are congruent
  • c)
    No, they are not congruent
  • d)
    Yes, by SSS Congruence theorem they are congruent
Correct answer is option 'D'. Can you explain this answer?

EduRev Class 9 answered
Let's analyze the given information step by step to determine whether triangles ΔABC and ΔPBC are congruent.
  1. Given:
    • AB = BP
    • AC = PC
    • BC = BC (common side)
  2. Triangles Involved:
    • ΔABC with sides AB, BC, and AC.
    • ΔPBC with sides PB (which is equal to AB), BC, and PC (which is equal to AC).
  3. Corresponding Sides:
    • AB corresponds to BP
    • AC corresponds to PC
    • BC corresponds to BC
  4. Applying the SSS Congruence Theorem:
    The Side-Side-Side (SSS) Congruence Theorem states that if all three corresponding sides of two triangles are equal in length, then the triangles are congruent.
    • AB = BP (First pair of corresponding sides)
    • AC = PC (Second pair of corresponding sides)
    • BC = BC (Third pair of corresponding sides, common side)
    Since all three pairs of corresponding sides are equal, ΔABC ≅ ΔPBC by the SSS Congruence Theorem.

Two equilateral triangles are congruent when:
  • a)
    Their areas are proportional
  • b)
    Their sides are equal
  • c)
    Their sides are proportional
  • d)
    Their angles are equal
Correct answer is option 'B'. Can you explain this answer?

EduRev Class 9 answered
Explanation: For two equilateral triangles to be congruent, their corresponding sides must be equal in length. In congruent triangles, all corresponding sides and angles are identical. While equilateral triangles always have equal angles (60°), congruence is specifically determined by the equality of sides.

Choose the correct statement
  • a)
    Two right triangles are congruent, if hypotenuse and a side of one are respectively equal to the hypotenuse and a side of the other triangle
  • b)
    If thee altitude from one vertex of a triangle bisects the opposite side, then the triangle may be isosceles
  • c)
    If any two sides of a right triangle are respectively are equal to two sides of the other right triangle, then the two triangles are congruent
  • d)
    Sides opposite equal angles may be unequal
Correct answer is option 'A'. Can you explain this answer?

Let's Tute answered
Answer: A
Explanation:
Option A is correct because the Hypotenuse-Side (HS) congruence criterion states that if the hypotenuse and one side of one right triangle are equal to the hypotenuse and one side of another right triangle, the two triangles are congruent.
Other options are incorrect:
  • B: This statement is partially correct but not universally true for all cases, as the altitude bisecting the opposite side guarantees an isosceles triangle only under specific conditions.
  • C: The congruence of two right triangles cannot be guaranteed if just any two sides are equal; the Hypotenuse-Leg or another criterion must be specified.
  • D: If the angles are equal, the opposite sides must also be equal, making this statement incorrect.

If the vertical angle of a isosceles triangle is 40°, then measure of other two angles will be
  • a)
    60°, 60°
  • b)
    80°, 80°
  • c)
    70°, 70°
  • d)
    45°, 45°
Correct answer is option 'C'. Can you explain this answer?

Akshara bajaj answered
**Explanation:**

An isosceles triangle is a triangle that has two sides of equal length. In an isosceles triangle, the angles opposite the equal sides are also equal.

Given that the vertical angle of the isosceles triangle is 40°, we can determine the measures of the other two angles.

Let the base angles of the isosceles triangle be x°. Since the triangle is isosceles, both base angles are equal.

**Step 1: Set up an equation:**
The sum of the angles in any triangle is always 180°. So, we can set up an equation to find the measure of the base angles.

x + x + 40° = 180°

Simplifying the equation:
2x + 40° = 180°

**Step 2: Solve for x:**
Subtract 40° from both sides of the equation:
2x = 180° - 40°
2x = 140°

Divide both sides of the equation by 2:
x = 70°

**Step 3: Find the measures of the other two angles:**
Since the base angles are equal, the measures of the other two angles in the isosceles triangle are both 70°.

Therefore, the correct answer is option C: 70°, 70°.

 An angle of measure 180° is called
  • a)
    a zero angle
  • b)
    a right angle
  • c)
    a straight angle
  • d)
     a reflex angle
Correct answer is option 'C'. Can you explain this answer?

Laksh Jain answered
The answer is (c) A straight angle....
because it is straight, and flat. if it is turned around a bit, it would become an obtuse or reflex angle.

What is the angle included between the sides PN and PM of ΔMNP?
  • a)
    ∠M
  • b)
    ∠N
  • c)
    ∠P
  • d)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Sorry, but I can't answer your question without more information. Can you please provide more context or specify what figure or shape you are referring to?

By which congruence rule following triangles are congruent ?
  • a)
    ASA
  • b)
    SSS
  • c)
    RHS
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Side-Side-Side (SSS) Rule
Side-Side-Side is a rule used to prove whether a given set of triangles are congruent.

The SSS rule states that:

If three sides of one triangle are equal to three sides of another triangle, then the triangles are congruent.

In the diagrams below, if AB = RP, BC = PQ and CA = QR, then triangle ABC is congruent to triangle RPQ.

ABCD is a parallelogram. If the two diagonals AC and BD are equal, then by what criterion are the triangles ABD and ABC congruent?
  • a)
    AAS
  • b)
    SSS
  • c)
    SAS
  • d)
    RHS
Correct answer is option 'B'. Can you explain this answer?

Imk Pathshala answered
Proof of Congruence
1. Given:
  • ABCD is a parallelogram.
  • Diagonals AC and BD are equal.
2. To Prove:
Triangles ABD and ABC are congruent.
3. Explanation:
  • In a parallelogram, if the diagonals are equal, then the parallelogram is a rectangle because only rectangles have equal diagonals.
  • Since ABCD is a rectangle, its diagonals bisect each other and are equal in length, meaning each half of the diagonal is also equal.
4. Congruence Criterion:
  • In triangles ABD and ABC:
    • AB is common to both triangles.
    • BD = AC, as they are equal diagonals of the rectangle.
    • AD = BC, as opposite sides of the rectangle are equal.
  • Thus, by the SSS (Side-Side-Side) criterion, △ABD ≅ △ABC.
Therefore, the triangles ABD and ABC are congruent by the SSS criterion.

In the below figure, AB = AC = CD. If ΔACD ≌ ΔABE then AD =
  • a)
    AC
  • b)
    AE
  • c)
    AB
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Ananya Das answered
ΔACD ≌ ΔABE. Here angle A corresponds to Angle A, Angle C with Angle B and Angle D with Angle E, Similarly Side AC corresponds to AB, CD to BE and AD to AE. So AE is the answer.

Which of the following sets of conditions does not guarantee that two triangles are congruent?
  • a)
    Two angles and a corresponding side are equal.
  • b)
    Two sides and the included angle are equal.
  • c)
    Two sides and a non-included angle are equal.
  • d)
    All three corresponding sides are equal.
Correct answer is option 'C'. Can you explain this answer?

Let's Tute answered
  • Option A: Describes the Angle-Angle-Side (AAS) condition, which does guarantee congruence.
  • Option B: Describes the Side-Angle-Side (SAS) condition, which does guarantee congruence.
  • Option C: Having two sides and a non-included angle equal only guarantees similarity, not necessarily congruence.
  • Option D: Describes the Side-Side-Side (SSS) condition, which does guarantee congruence.
  • Hence, option C is the answer

In the below figure, AC = BD and AD = BC. Which of the following statements is meaningfully written? 
  • a)
    ΔABC ≅ ΔBAD
  • b)
    ΔABC ≅ ΔBDA
  • c)
    ΔABC ≅ ΔADB
  • d)
    ΔABC ≅ ΔABD
Correct answer is option 'A'. Can you explain this answer?

Arnab Sen answered
AC corresponds to BD and AD corresponds to BC. So while writing the name of the triangles the alphabets should be written according to the correspondence. So ΔABC ≅ ΔBAD

In the given figure, AB = PQ, BC = QR and the median AD is equal to the median PM of the other triangle PQR, then ΔABD is congruent  ΔPQM by the criterion
  • a)
    AAS
  • b)
    SSS
  • c)
    RHS
  • d)
    SAS
Correct answer is option 'B'. Can you explain this answer?

EduRev Class 9 answered
We are asked to prove that triangle ABD is congruent to triangle PQM.
Step 1: Compare given information
  • AB = PQ (given)
  • BC = QR (given)
  • AD = PM (given, both are medians)
Step 2: Use property of medians
  • Since AD is the median of triangle ABC, point D is the midpoint of BC.
    So BD = DC = half of BC.
  • Since PM is the median of triangle PQR, point M is the midpoint of QR.
    So QM = MR = half of QR.
Step 3: Use the equality of sides
  • From given, BC = QR.
  • Therefore, half of BC = half of QR.
  • This means BD = QM.
Step 4: Now check corresponding sides of triangles ABD and PQM
  • In triangle ABD and triangle PQM:
  1. AB = PQ (given)
  2. BD = QM (proved using medians and BC = QR)
  3. AD = PM (given)
So, all three sides of triangle ABD are equal to the corresponding three sides of triangle PQM.
Step 5: Congruence criterion
  • When three sides of one triangle are equal to the three sides of another triangle, the two triangles are congruent by the SSS (Side-Side-Side) criterion.
Final Answer: The correct option is b) SSS.

PQRS is a parallelogram, if the two diagonals are equal, then the measure of PQR is:
  • a)
    30°
  • b)
    90°
  • c)
    60°
  • d)
    120°
Correct answer is option 'B'. Can you explain this answer?

EduRev Class 9 answered
In a parallelogram, the diagonals are equal if and only if the parallelogram is a rectangle. This is because equal diagonals imply that the opposite angles are equal, and the only type of parallelogram where this happens is a rectangle.
In a rectangle, all angles are 90. Therefore, the measure of ∠PQR is: 90.

In the following figure, PT is the bisector of ___________.
  • a)
    ∠QPR
  • b)
    QTR
  • c)
    Both A and B option 
  • d)
    None of these
Correct answer is option 'C'. Can you explain this answer?

EduRev Class 9 answered
as QT = TR and QP = PR
then  QT/QP = TR/PR
so PT would be internal bisector of ∠QPR
and as QT = TR, 
hence , T is the bisector of QTR as well.
Therefore, both A and B

In triangles ABC and PQR, AB = 3.5 cm, BC = 7.1 cm, AC = 5 cm, PQ = 7.1 cm, QR = 5 cm and PR = 3.5 cm, then which of the following is true
  • a)
    ΔABC ≅ Δ PQR
  • b)
    ΔABC ≅ Δ QRP
  • c)
    ΔABC ≅ Δ RPQ
  • d)
    ΔABC ≅ Δ QPR
Correct answer is option 'C'. Can you explain this answer?

Coachify answered
In triangle ABC, the side lengths are AB = 3.5 cm, BC = 7.1 cm, and AC = 5 cm. In triangle RPQ, the corresponding side lengths are RP = 3.5 cm, PQ = 7.1 cm, and RQ = 5 cm. Since each side of triangle ABC is equal to the corresponding side of triangle RPQ, the triangles satisfy the Side-Side-Side (SSS) congruence criterion. Therefore, triangle ABC is congruent to triangle RPQ.

The measure of each angle of an equilateral triangle is:
  • a)
    50°
  • b)
    70°
  • c)
    60°
  • d)
    100°
Correct answer is option 'C'. Can you explain this answer?

Hitakshi Arora answered
Let the each angle of triangle be 't'.
3 t = 180
t = 180 ÷ 3 ( 60 x 3=180 )
t = 60
Hence, the correct option is c) 60

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