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All questions of The Triangles and its properties for Class 7 Exam

  • a)
    50°
  • b)
    120°
  • c)
    110°
  • d)
    30°
Correct answer is 'A'. Can you explain this answer?

Exterior angle is equal to opposite interior angle so, when we add 50 degree to 30 it will come 80 degree .. that 'A' is correct

The altitude and median be same for a which triangle?
  • a)
    Scalene triangle
  • b)
    Equilateral triangle
  • c)
    Acute
  • d)
    Right
Correct answer is option 'B'. Can you explain this answer?

Sparsh Khanna answered
In an equilateral triangle, both the median and the altitude are the same. This is because the perpendicular line drawn from the vertex of the triangle to the base cuts it equally. Also in the isosceles triangle, altitude and median are the same.

Find the value of x.
  • a)
    110°
  • b)
    60°
  • c)
    70°
  • d)
    50°
Correct answer is option 'B'. Can you explain this answer?

Rohini Seth answered
An exterior angle of a triangle is equal to the sum of the opposite interior angles
So in the given figure 
110o = 50o + x 
110o - 50o = x 
60o = x 
So option B is correct answer. 

Can you explain the answer of this question below:
How many medians a triangle can have?
A:1
B:2
C:3
D:none of these
The answer is C.

Sneha Khanna answered
In geometry, a median of a triangle is a line segment joining a vertex to the midpoint of the opposite side, thus bisecting that side. Every triangle has exactly three medians, one from each vertex, and they all intersect each other at the triangle's centroid.

  • a)
    60°
  • b)
    50°
  • c)
    120°
  • d)
    70°
Correct answer is option 'C'. Can you explain this answer?

Rahul Shah answered
An exterior angle of a triangle is equal to the sum of the opposite interior angles
x deg = 70 deg + 50 deg
x deg = 120 deg .
So option C is the correct answer. 

In ΔPQR, PD is
  • a)
    Altitude
  • b)
    Bisector
  • c)
    side
  • d)
    Median
Correct answer is option 'D'. Can you explain this answer?

Median is a line joining the vertex and middle of the opposite side, and hence dividing the triangle in two equal parts. So PD is the median.

  • a)
    50°
  • b)
    60°
  • c)
    180°
  • d)
    120°
Correct answer is option 'B'. Can you explain this answer?

Exterior angle is equal to sum of interior opposite angles so,
120 = 60+x
x = 60°

Vertex opposite to the side RT of ΔRST is 
  • a)
    T
  • b)
    S
  • c)
    R
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Geetika Shah answered
The vertex opposite to side RT is S.
Step-by-step explanation:
In the given question,
We have a triangle RST which has sides RS, ST and TR.
We know that a triangle consists three vertices and three sides each of which is particularly opposite to any one of the side of the triangle and vice-versa.
Therefore, we can see here that in the triangle RST.
The side RS is opposite to the vertex T.
The side ST is opposite to the vertex R.
and,
The side TR is opposite to the vertex S.
Hence, the correct answer will be S as side RT is opposite to S.

The value of x in the adjoining figure is
  • a)
    15°
  • b)
    90°
  • c)
    30°
  • d)
    45°
Correct answer is option 'D'. Can you explain this answer?

as two sides are equal so it is a isoceles triangle with one angle as 90° so other remaining two will be
each 45° 

A triangle in which all three sides are of equal lengths is called _________.
  • a)
    Scalene
  • b)
    Isosceles
  • c)
    Equilateral
  • d)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Kritika nair answered
Equilateral Triangle
An equilateral triangle is a type of triangle in which all three sides are of equal lengths. It is a special case of a regular polygon, where all sides and angles are equal. In an equilateral triangle, all three angles are also equal to 60 degrees.

Characteristics of an Equilateral Triangle
- All three sides of an equilateral triangle are of equal length.
- All three angles of an equilateral triangle are equal to 60 degrees.
- The sum of the interior angles of an equilateral triangle is always 180 degrees.
- The altitude, median, and perpendicular bisectors of an equilateral triangle are concurrent.
- The circumcenter, incenter, and centroid of an equilateral triangle coincide and are the same point.
- The area of an equilateral triangle can be calculated using various formulas, such as A = (s^2 * √3) / 4, where s is the length of a side.

Visual Representation
To visualize an equilateral triangle, imagine a triangle with all three sides of equal length. Each angle of the triangle measures 60 degrees. It appears symmetrical and balanced.

Distinguishing from Other Types of Triangles
- Scalene Triangle: In a scalene triangle, all three sides have different lengths. Therefore, it is not an equilateral triangle.
- Isosceles Triangle: In an isosceles triangle, two sides have the same length, while the third side is of a different length. Since all three sides of an equilateral triangle are equal, it is not an isosceles triangle either.

Importance of Equilateral Triangles
- Equilateral triangles are commonly used in architecture and engineering because of their symmetry and stability.
- They are often found in the design of bridges, buildings, and other structures.
- The properties of equilateral triangles are used in various mathematical and geometrical calculations.
- They are also used in various puzzles and games.

Conclusion
An equilateral triangle is a special type of triangle in which all three sides are of equal lengths. It possesses unique properties and characteristics that distinguish it from other types of triangles. Equilateral triangles have practical applications in various fields and are important in mathematical and geometrical concepts.

What is the measure of angles x?
  • a)
    30°
  • b)
    60°
  • c)
    90°
  • d)
    45°
Correct answer is option 'C'. Can you explain this answer?

Anita Menon answered
Since the two sides are equal, the angles opposite to them are also equal.
So x + 45° + 45° = 180° (Angles sum property)
x = 90°

Which is the longest side in the triangle PQR right angled at P?
  • a)
    PQ
  • b)
    QR
  • c)
    PR
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?

QR because in a right angled triangle hypotenuse is the biggest line and here point P is 90 degrees so the QR line would make hypotenuse

Find the value of unknown x in the adjoining figure.
  • a)
    60°
  • b)
    80°
  • c)
    45°
  • d)
    70°
Correct answer is option 'D'. Can you explain this answer?

Correct answer is option d because:-

Total perimeter of the triangle is 180 degree
= x+50+60=180
50+60=110
110-180
=70 degree

So please this is explained answer please followed.

please

If the angles of a triangle are in the raitio 4:5:9. Find all the angles of a the triangle
  • a)
     
    40 deg, 50 deg , 90 deg 
     
  • b)
    90 deg, 72 deg, 18 deg
  • c)
    9 deg, 90 deg, 55 deg
  • d)
    45 deg, 60 deg, 18 deg 
Correct answer is option 'A'. Can you explain this answer?

Dipanjan Goyal answered
The sum of the angles of a triangle is 180 degrees. As the ratio of the angles of the triangle is 4:5:9 they can be taken to be 4x, 5x and 9x. 4x + 5x + 9x = 180
=> 18x = 180
=> x = 10
This gives the angles of the triangle as 40, 50 and 90 degrees.

Which type of triangle is formed by BC=7.2cm, AC=6 cm and ∠120o?
  • a)
    An obtuse angled triangle.  
  • b)
    An acute angled triangle.
  • c)
    A right angled triangle.
  • d)
    An isosceles triangle.
Correct answer is option 'A'. Can you explain this answer?

Yashvi Singh answered
Understanding the Triangle Inequality Theorem

The statement in the question refers to the Triangle Inequality Theorem, which states that the sum of the lengths of any two sides of a triangle is always greater than the length of the third side. This theorem is a fundamental concept in geometry and is applicable to all types of triangles, including equilateral, isosceles, and scalene triangles.

Explanation of the Triangle Inequality Theorem

To understand why the sum of the lengths of any two sides is greater than the length of the third side, we need to consider the possible scenarios that can occur when constructing a triangle.

Scenario 1: The sum of the lengths of two sides is equal to the length of the third side
In this scenario, when the sum of the lengths of two sides of a triangle is equal to the length of the third side, the three sides are said to be in a straight line, and the triangle is called a degenerate triangle. In such a case, the triangle collapses into a line segment, and it is not considered a valid triangle.

Scenario 2: The sum of the lengths of two sides is less than the length of the third side
In this scenario, when the sum of the lengths of two sides is less than the length of the third side, it is impossible to construct a triangle. When we try to connect the two shorter sides, they will not meet to form a closed figure.

Scenario 3: The sum of the lengths of two sides is greater than the length of the third side
In this scenario, when the sum of the lengths of two sides is greater than the length of the third side, it is possible to construct a triangle. When we try to connect the two shorter sides, they will meet to form a closed figure, and all three sides will be connected.

Conclusion

Based on the Triangle Inequality Theorem, we can conclude that the sum of the lengths of any two sides of a triangle is always greater than the length of the third side. This theorem is essential in determining whether a given set of side lengths can form a valid triangle or not. Therefore, option 'A' - greater than, is the correct answer.

In the figure (not drawn to scale), ABCD is a square, ADE is an equilateral triangle and BFE is a straight line, find y. 
  • a)
    90o
  • b)
    45o
  • c)
    75o
  • d)
    15o
Correct answer is option 'C'. Can you explain this answer?

Mrinalini Shah answered
In ΔAEB, 

 ∠A=∠DAE+∠BAD ⇒ ∠A=60o+90o=15
And,  AE=AB ⇒ ∠ABE=∠AEB  
[Angles opposite to equal sides are equal]
Now, ∠A+∠ABE+∠AEB=180  (Angle sum property) 
⇒ 2∠AEB=180−150= 30o ⇒ ∠AEB = 15 
Now, ∠E=60⇒ ∠DEF=60o−15= 45
∴ In ΔEFD, ∠DEF+∠EDF+∠EFD
= 180⇒ 45o+60o+y = 180
⇒ y = 180o−(45o+60o) = 75o

Find angle x in
  • a)
    60°
  • b)
    160°
  • c)
    80°
  • d)
    100°
Correct answer is option 'A'. Can you explain this answer?

Sum of interior opposite angles = Exterior angle
or 50° + x = 110°
or x = 60°

If the two legs of a right angled triangle are equal and the square of the hypotenuse is 100 sq units, what is the length of each leg?
  • a)
    10 units
  • b)
    5√2 units  
  • c)
    10√2 units
  • d)
    15 units
Correct answer is option 'B'. Can you explain this answer?

Let's solve the problem step by step:
Given:
  • The two legs of a right-angled triangle are equal.
  • The square of the hypotenuse is 100 square units.
Let the length of each leg be x units.
Using the Pythagorean theorem:
 

Find the measure of ∠LNM in the given figure.
  • a)
    30                   
  • b)
    80o                    
  • c)
    70o                 
  • d)
    60o
Correct answer is option 'D'. Can you explain this answer?

Kunal Mehra answered
∠KLO = ∠MLN 
∴ ∠MLN = 70o in ∠LMN
Also, 
∠MLN+∠LNM+∠LMN = 180(Angle sum property) 
⇒ 70o+∠LNM+50o=180o
 
⇒ ∠LNM = 180o−(70o+50o) = 60o

Classify the following triangle on basis of their sides 
  • a)
    (i)scalene, (ii) isoceles, (iii) equilateral 
  • b)
    (i) isosceles, (ii) right, (iii) equilateral 
  • c)
    (i) right, (ii) isosceles, (iii) equilateral 
  • d)
    (i) equilateral, (ii) scalene, (iii) isosceles
Correct answer is option 'A'. Can you explain this answer?

(i) PQ = 5 cm, PR = 6 cm and QR = 7 cm
PQ ≠ PR ≠ QR
Thus, ∆PQR is a scalene triangle.
(ii) AB = 4 cm, AC = 4 cm, BC = 4.5 cm
AB = AC ≠ 4.5 cm
Thus, ∆ABC is an isosceles triangle.
(iii) MN = 3 cm, ML = 3 cm and NL = 3 cm
MN = ML = NL
Thus, ∆MNL is an equilateral triangle.

In the figure (not drawn to scale), ABC is an equilateral triangle and ABD is an isosceles triangle with DA = DB, find x. 
  • a)
    14o                    
  • b)
    16                   
  • c)
    12o             
  • d)
    32o    
Correct answer is option 'A'. Can you explain this answer?

Anmol Iyer answered
Since ABC is an equilateral triangle. 
∴ ∠CAB =∠ABC =∠BCA = 60 
And ∠DBA = ∠DAB = (60o−x) 
[∵ DA = DB] 
In ΔDAB, ∠DBA+∠DAB+∠ADB =180  (Angle sum Property)
⇒ 2(60o−x)+88= 180o 
⇒ 2(60o−x) = 92o
⇒ 60o−x = 46⇒ x = 14o

If a triangle has angles measuring 40°, 60°, and x°, find the value of x.
  • a)
    70°
  • b)
    80°
  • c)
    90°
  • d)
    100°
Correct answer is option 'B'. Can you explain this answer?

Kds Coaching answered
The sum of all angles in a triangle is always 180°.
40° + 60° + x = 180°
x = 180° - (40° + 60°)
x = 180° - 100° = 80°

Find value of angle 1, 2, and 3, where angle y is equal to angle 3
  • a)
    60 degrees 
  • b)
    70 degrees 
  • c)
    140 degrees 
  • d)
    20 degrees 
Correct answer is option 'A'. Can you explain this answer?

Kds Coaching answered
Adding both sides, we have:
∠y + ∠1 + ∠2 = 3∠x
Therefore, 180° = 3∠x (Angle sum property of a triangle)
So,∠x = 180° ÷ 3 = 60°
∠x = 60°, ∠y = 60°
Therefore, the value of all angles is 60° and it is an equilateral triangle

In ΔABC, AC = BC and ∠C = 110°. Find ∠A and ∠B.
  • a)
    35°
  • b)
    75°
  • c)
    45°
  • d)
    105°
Correct answer is option 'A'. Can you explain this answer?

In given ΔABC, ∠C = 110°
Let ∠A = ∠B = x° (Angle opposite to equal sides of a triangle are equal)
x + x + 110° = 180° (Sum of all angles in a triangle is 180°)
⇒ 2x + 110° = 180°
⇒ 2x = 180° – 110°
⇒ 2x = 70°
⇒ x = 35°
Thus, ∠A = ∠B = 35°

Side opposite to the vertex Q of ΔPQR is 
  • a)
    PQ
  • b)
    QR
  • c)
    PR
  • d)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Kds Coaching answered
In Triangle ΔPQR, the side opposite to vertex Q is the side that does not touch vertex Q.
The side opposite to Q would be side PR, as it does not include the vertex Q.
for example, 

Chapter doubts & questions for The Triangles and its properties - Mathematics (Maths) Class 7 2025 is part of Class 7 exam preparation. The chapters have been prepared according to the Class 7 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Class 7 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

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