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All questions of Triangles for SSS 1 Exam

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Which geometric figures are always similar?​
  • a)
    Circles
  • b)
    Circles and all regular polygons
  • c)
    Circles and triangles
  • d)
    Regular polygons
Correct answer is option 'B'. Can you explain this answer?

Raghav Bansal answered
It can be found that circles map one  onto another.So they are similar figures. A regular polygon is a polygon which has the same sides and equal measures of angles. So they are also similar.

In triangle ABC, if AB = 6√3 cm, AC = 12 cm and BC cm, then ∠B is 
  • a)
    120°
  • b)
    60°
  • c)
    90°
  • d)
    45°
Correct answer is option 'C'. Can you explain this answer?

Gaurav Kumar answered
Here largest side is 12 cm. 
If the square of the hypotenuse is equal to the square of the other two sides, then it is a right-angled triangle. 
∴ c2 = a2 + b2 
AC2 = AB2 + BC2
(12)2 = (63)2 + (6)2
44 = 36 × 3 + 36 
144 = 108 + 36 
144 = 144 
∴ ∆ABC is a right angled triangle and angle opposite to hypotenuse, ∠B = 90°.

ΔABC ~ ΔPQR, ∠B = 50° and ∠C = 70° then ∠P is equal to​
  • a)
    50°
  • b)
    60°
  • c)
    40°
  • d)
    70°
Correct answer is option 'B'. Can you explain this answer?

Radha Iyer answered
Similar triangles have corresponding angles equal. So Angle Q=Angle B = 50° and Angle R = Angle C = 70° . So by angle sum property, Angle P+Angle Q +Angle R = 180°
Angle P=180° - 50° - 70° = 60°

In an equilateral triangle ABC, if AD ⊥ BC. Then​
  • a)
    3AB2 = 4AD2
  • b)
    2AB2 = 3AD2
  • c)
    3AB2 = 2AD2
  • d)
    4AB2 = 3AD2
Correct answer is option 'A'. Can you explain this answer?

Raghav Bansal answered
∆ ABC, in which sides are AB=BC= AC= a units and AD is perpendicular to BC ,
In ∆ADB ,
AB²= AD²+ BD²     (by Pythagoras theorem)
a² = AD² + (a/2)²   [BD= 1/2BC, since in an equilateral triangle altitude AD is  perpendicular bisector of BC ]
a²- a²/4 =AD²
⇒ ( 4a²-a²)/4 = AD²
⇒ 3a² /4 = AD²
⇒ 3AB²/4= AD²               [ AB= a]
⇒  3AB²= 4AD²

 Two congruent triangles are actually similar triangles with the ratio of corresponding sides as.​
  • a)
    1:2
  • b)
    1:1
  • c)
    1:3
  • d)
    2:1
Correct answer is option 'B'. Can you explain this answer?

Similar Triangles and Corresponding Sides

Similar triangles are those triangles that have the same shape but may have different sizes. When two triangles are similar, the corresponding angles are the same, and the corresponding sides are proportional. In other words, the ratio of the lengths of the corresponding sides is the same for all pairs of corresponding sides. This ratio is called the scale factor.

Given the statement that "Two congruent triangles are actually similar triangles with the ratio of corresponding sides as," we are asked to determine the scale factor for the corresponding sides of the two triangles.

Option B is the correct answer, and the scale factor is 1:1. This means that the corresponding sides of the two triangles are equal in length.

Explanation of Other Options:

a) 1:2 - This means that the corresponding sides of one triangle are twice as long as the corresponding sides of the other triangle. Therefore, the triangles are not congruent, but they are similar.

c) 1:3 - This means that the corresponding sides of one triangle are three times as long as the corresponding sides of the other triangle. Therefore, the triangles are not congruent, but they are similar.

d) 2:1 - This means that the corresponding sides of one triangle are half as long as the corresponding sides of the other triangle. Therefore, the triangles are not congruent, but they are similar.

Conclusion:

In summary, when two triangles are congruent, they are also similar with a scale factor of 1:1. This means that the corresponding sides of the triangles are equal in length.

In the following figure, find the value of x.
  • a)
    65°
  • b)
    70°
  • c)
    80°
  • d)
    30°
Correct answer is option 'B'. Can you explain this answer?

Arun Sharma answered
The triangles are similar by SAS criterion, So we have, Angle A+Angle B + Angle C=180
x=180-30-80=70 degrees 

 If ΔDEF ~ ΔABC and DE=AB, what is the relation between the two triangles?​
  • a)
    They are both right triangles.
  • b)
    ΔDEF ≠ ΔABC
  • c)
    They are both equilateral.
  • d)
    ΔDEF ≅ ΔABC
Correct answer is option 'D'. Can you explain this answer?

Naina Sharma answered
Since DE=AB means that there ratio is 1 which means corresponding sides are equal.Two triangles are said to be similar if their corresponding angles are congruent and the corresponding sides are in proportion . In other words, similar triangles are the same shape, but not necessarily the same size. The triangles are congruent if, in addition to this, their corresponding sides are of equal length.So they are congruent.

D and E are respectively the points on the sides AB and AC of a triangle ABC such that AD = 3 cm, BD = 5 cm, BC = 12.8 cm and DE || BC. Then length of DE (in cm) is
  • a)
    4.8 cm
  • b)
    7.6 cm
  • c)
    19.2 cm
  • d)
    2.5 cm
Correct answer is option 'A'. Can you explain this answer?

Meera Rana answered
GIVEN: In  Δ ABC, D and E are points on AB and AC , DE ||  BC and  AD = 2.4 cm, AE = 3.2 cm, DE = 2 cm and BE = 5 cm.
In Δ ADE and Δ ABC,
∠ADE =∠ABC    (corresponding angles)
[DE || BC, AB is transversal]
∠AED =∠ACB     (corresponding angles)
[DE || BC, AC is transversal]
So, Δ ADE  ~ Δ ABC      (AA similarity)
Therefore, AD/AB = AE/AC = DE/BC
[In similar triangles corresponding sides are proportional]
AD/AB = DE/BC
2.4/(2.4+DB)  = 2/5
2.4 × 5  = 2(2.4+ DB)
12 = 4.8 + 2DB
12 - 4.8  = 2DB
7.2 = 2DB
DB = 7.2/2  
DB = 3.6 cm
Similarly, AE/AC = DE/BC
3.2/(3.2+EC) = 2/5
3.2 × 5 = 2(3.2+EC)
16 = 6.4 + 2EC
16 - 6.4 = 2EC
9.6 = 2EC
EC = 9.6/2
EC = 4.8 cm
Hence,BD = 3.6 cm and CE = 4.8 cm.

If PQR is an isosceles triangle and M is a point on QR such that PM⊥QR,then
  • a)
    PQ2−PM2 = QM2−MR2.
  • b)
    PQ2+PM2 = QM.MR.
  • c)
    PQ2−PR2 = QM2 − MR2
  • d)
    PQ2−PM2 = QM.MR.
Correct answer is option 'C'. Can you explain this answer?

Krishna Iyer answered
 
Since, in a triangle the sum of squares of any wo sides is equal to twice the square of half of the third side together with twice the square of the median bisecting it.
In ΔPQM,

 ΔABC ~ ΔDEF Perimeter( ΔABC )= 15 cm, Perimeter( DEF )=25 cm.If AB= 6 cm, then find DE.
  • a)
    14
  • b)
    12
  • c)
    10
  • d)
    16
Correct answer is option 'C'. Can you explain this answer?

Gaurav Kumar answered
Ratios of perimeter of similar triangles are equal to the ratio of their sides.
So Perimeter of ABC/perimeter of DEF=15/25=⅗
AB/DE=⅗
DE=6*5/3=10

In triangles ABC and DEF, ∠B = ∠E, ∠F = ∠C and AB = 3DE. Then, the two triangles are
  • a)
    congruent but not similar
  • b)
    similar but not congruent
  • c)
    neither congruent nor similar
  • d)
    congruent as well as similar
Correct answer is option 'B'. Can you explain this answer?

Kiran Mehta answered
to be congruent, the conditions are
S S S - three sides
S A S - two sides and the included angle
A S A - two angles and one side
R H S - R H S - Right angle, Hypotenuse and one side
But to be similar,
A A A means 3 angles
A A means only two angles ....
in both triangles should be equal.
In the problem, equality of two angles is given, but equality of sides is not given.
So, given triangles are not congruent.
But they are similar.

In the adjoining figure D, E and F are the mid-points of the sides BC, AC and AB respectively. ΔDEF is congruent to triangle :
  • a)
    ABC
  • b)
    AEF
  • c)
    AFE, BFD and CDE
  • d)
    CDE , BFD
Correct answer is option 'C'. Can you explain this answer?

Raghav Bansal answered
Given :△ABC, F, D and E are mid points of AB, BC, CA respectively.
Using mid point theorem we prove that □AEFD, □DBFF and □DCEF are parallelograms. The diagonal of a parallelogram divides the parallelogram into two congruent triangles. So all triangles are congruent to each other. So ΔDEF is congruent to 
△AFE, △BFD and △CDE

 If ΔPQR ~ ΔXYZ , ∠Q = 50° , ∠R = 70° then ∠X is equal to :​
  • a)
    50°
  • b)
    60°
  • c)
    70°
  • d)
    120°
Correct answer is option 'B'. Can you explain this answer?

Yogita Rishi answered
Angle Q = 50
Angle R= 70
Angle p = ?
now
we know that the angle sum property of a triangle is equal to 180 degree
Angle Q + angle R+ angle P = 180
50 + 70 + angle P = 180
120 + angle P = 180
angle P = 180 - 120
-Angle p = 60
as they both are similar so by corresponding parts of similar triangle
Angle P = Angle X
Angle x = 60....

 In the figure given below, if DE || BC, then x equals :
  • a)
    2 cm
  • b)
    4 cm
  • c)
    6.7 cm
  • d)
    3 cm
Correct answer is option 'C'. Can you explain this answer?

Pooja Shah answered
We have Angle ADE= Angle ABC
And ANGLE A is common, So by AA criterion of similarity the two triangles are similar so AD/AB=DE/BC
x=5*4/3=6.7

  • a)
    ∠B=∠D.
  • b)
    ∠B=∠E.
  • c)
    ∠A=∠D.
  • d)
    ∠A=∠F.
Correct answer is option 'A'. Can you explain this answer?

Manisha reddy answered
Given information:
- QR < 2pq="" -="" />
- PR = PQ + 10
- Perimeter = 40

To find:
- Smallest side of the triangle PQR

Solution:
Let's assume that PQ = x, QR = y, and PR = z.

Using the given information, we can write two equations based on the lengths of the sides:

1. y = 2x - 2 (QR is less than twice the length of PQ by 2 cm)
2. z = x + 10 (PR exceeds the length of PQ by 10 cm)

We also know that the perimeter of the triangle is 40 cm:

x + y + z = 40

Substituting the values of y and z from equations (1) and (2) into equation (3), we get:

x + (2x - 2) + (x + 10) = 40

Simplifying the equation, we get:

4x + 8 = 40

4x = 32

x = 8

Therefore, the length of the smallest side of the triangle PQR is PQ = x = 8 cm.

Answer: Option (B) 8 cm.

In the given figure, AD/BD = AE/EC and ∠ADE = 70°, ∠BAC = 50°, then angle ∠BCA =
  • a)
    70°
  • b)
    50°
  • c)
    80°
  • d)
    60°
Correct answer is option 'D'. Can you explain this answer?

Trisha sharma answered
Explanation:
By converse of Thale’s theorem DE II BC  
∠ADE = ∠ABC = 70 degree  
Given ∠BAC = 50 degree

You can read Important Definitions & Formulas related to Triangles through the document: 

The areas of two similar triangles are 100cmand 49 cm2. If the altitude of the larger triangle is 5 cm, then the corresponding altitude of the other triangle is equal to
  • a)
    3.5 cm.
  • b)
    3.9 cm.
  • c)
    5.4 cm.
  • d)
    4.5 cm.
Correct answer is option 'A'. Can you explain this answer?

Krishna Iyer answered
Let the two similar triangles be ΔABC and ΔDEF such that ar(ΔABC) = 100 cm2 and ar(ΔDEF) = 49 cm2.
Let AM and DN be the respective altitudes of ΔABC and ΔDEF.
Since the ratio of the areas of two similar triangles is equal to the ratio of the squares of their corresponding altitudes

If ΔABC ~ ΔEDF  then which of the following is not true?
  • a)
    BC . EF = AC . FD
  • b)
    AB . EF = AC . DE
  • c)
    BC . DE = AB . EF 
  • d)
    BC . DE = AB . FD
Correct answer is option 'C'. Can you explain this answer?

Anita Menon answered
Since △ABC~△EDF
Then, AB/ED = BC/DF = AC/EF
A) BC/DF = AC/EF
⇒BC.EF=AC.FD   
So, A) is true
 
B) AB/ED = AC/EF
⇒AB.EF=AC.DE     
So,B) is true
 
D) AB/ED = BC/DF
BC.DE=AB.EF    
So, D) is not true
 
Therefore, Option  C is not true

In triangle MNS, A and B are points on the sides MN, NS respectively.  Then AB is …………………. to NS :​
  • a)
    Not Perpendicular
  • b)
    Parallel
  • c)
    Perpendicular
  • d)
    Not Parallel
Correct answer is option 'B'. Can you explain this answer?

Anita Menon answered
In ∆MNS we have,
→ AN = 1/2(MN)
→ AN = (1/2)(MA + AN)
→ AN = (1/2)MA + (1/2)AN
→ AN - (1/2)AN = (1/2)MA
→ AN[1 - (1/2)] = (1/2)MA
→ (1/2)AN = (1/2)MA
→ AN = MA
so, A is mid point of MN .
similarly,
→ BS = (1/2)(MS)
so, B is mid point of MS .
since AB is a line segment joining the mid points of two sides of ∆MNS .
therefore, → AB || NS { According to Mid point theorem the line segment joining the mid points of two sides of a triangle is parallel to the third side . }

Triangle ABC is an isosceles right triangle right angled at B.DE is a line parallel to BC which intersects AB in D and AC in E.What ratio are the sides of triangle ADE in?
  • a)
    3:4:5
  • b)
    1:1:1
  • c)
    1:1:√2
  • d)
    1:√3:2
Correct answer is option 'C'. Can you explain this answer?

Pooja Shah answered
Since AB =BC and the triangles are similar, AB/AD=BC/DE
Gives AD=DE
So by Pythagoras theorem, 
H2 = P2 + B2
H= 2x2
H = √2x
So the sides are in the ratio x:x: √2x which is 1:1: √2

The line segments joining the mid points of the sides of a triangle form four triangles each of which is :
  • a)
    Similar to the original triangle
  • b)
    Congruent to the original triangle
  • c)
    An equilateral triangle
  • d)
    An isosceles triangle
Correct answer is option 'A'. Can you explain this answer?

Krishna Iyer answered
Given :△ABC, D, E and F are mid points of AB, BC, CA respectively.
Using mid point theorem we prove that □ADEF, □DBEF and □DECF are parallelograms. The diagonal of a parallelogram divides the parallelogram into two congruent triangles. So all triangles are congruent to each other. And each small triangle is similar to the original triangle.

A square and a rhombus are always 
  • a)
    similar
  • b)
    congruent
  • c)
    similar but not congruent
  • d)
    neither similar nor congruent
Correct answer is option 'D'. Can you explain this answer?

Ishan Yadav answered
Square and Rhombus

A square is a four-sided polygon with all sides equal in length and all angles equal to 90 degrees. A rhombus is also a four-sided polygon with all sides equal in length, but its opposite angles are equal, and they do not necessarily equal 90 degrees.

Similarity and Congruence

Similarity and congruence are two important concepts in geometry. Similar figures have the same shape but different sizes, while congruent figures have the same shape and size.

Square and Rhombus Similarity

A square and a rhombus are not always similar. Although a square and a rhombus both have four sides of equal length, they have different angles. A square has four right angles of 90 degrees each, while a rhombus has two acute angles and two obtuse angles.

Square and Rhombus Congruence

A square and a rhombus are not always congruent. While they both have four sides of equal length, their angles are different. A square has four right angles of 90 degrees each, while a rhombus has two acute angles and two obtuse angles.

Conclusion

In conclusion, a square and a rhombus are neither similar nor congruent because they have different angles, despite having equal sides. Therefore, the correct answer is option D.

In ΔABC, AB = 3 cm, AC = 4 cm and AD is the bisector of ∠A. Then, BD : DC is :
  • a)
    9 : 16
  • b)
    16 : 9
  • c)
    3 : 4
  • d)
    4 : 3
Correct answer is option 'C'. Can you explain this answer?

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In the given figure ΔABC ~ ΔBDC = 90° each. Choose the correct similarity from the given choices.
  • a)
    ΔABC ~ ΔCBD
  • b)
    ΔABC ~ ΔDCB
  • c)
    ΔABC ~ ΔBCD
  • d)
    ΔABC ~ ΔBDC
Correct answer is option 'D'. Can you explain this answer?

Naina Sharma answered
We have Angle C common and Angle B = Angle D
So in similarity we write the name of the triangle in such an order in which the corresponding alphabets denote equal angles . this means that ΔABC ~ ΔBDC that says Angle A = Angle B, Angle B = Angle D, and Angle C = Angle C

In right triangle ABC, right angled at A,
A perpendicular is dropped from A to BC, meeting BC at D. Then which of the following is true?​
  • a)
    ΔADC ~ ΔABD
  • b)
    ΔDCA ~ ΔDABD
  • c)
    ΔDAC ~ ΔDABD
  • d)
    ΔDAC ~ ΔDABA
Correct answer is option 'D'. Can you explain this answer?

Naina kapoor answered
Explanation:

  • Let's draw the diagram first.

  • From the diagram, we can see that triangle ABD and triangle ACD are both right triangles.

  • Therefore, we can use the Pythagorean theorem to find their sides.

  • Let's assume that AB = b, AC = c, and BC = a.

  • Using Pythagorean theorem, we get:


    • AB² + BD² = AD² (for triangle ABD)

    • AC² + CD² = AD² (for triangle ACD)

    • BC² = AB² + AC² (by Pythagoras theorem)


  • Now, we can simplify the above equations to get:


    • BD² = AD² - AB² = (AC² + CD²) - AB²

    • CD² = AD² - AC² = (AB² + BD²) - AC²


  • Substituting the value of BD² and CD² in the above equations, we get:


    • AB² + (AC² + CD² - AB²) = AD²

    • AC² + (AB² + BD² - AC²) = AD²


  • After simplifying, we get:


    • AC² = AD² - AB²

    • AB² = AD² - AC²


  • Therefore, we can say that triangle DAC is similar to triangle DAB by the Angle-Angle-Similarity criterion.

  • Thus, option D is the correct answer.

In ΔPQR, ∠P = 60°, ∠Q = 50°. Which side of the triangle is the longest ?
  • a)
    PQ
  • b)
    QR
  • c)
    PR
  • d)
    none
Correct answer is option 'A'. Can you explain this answer?

Rohini sharma answered
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Chapter doubts & questions for Triangles - Mathematics for SSS 1 2024 is part of SSS 1 exam preparation. The chapters have been prepared according to the SSS 1 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for SSS 1 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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