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All questions of Pythagoras’ Theorem for Grade 8 Exam

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

Yash Kapoor answered
An exterior angle of a triangle is equal to the sum of the opposite interior angles
So in the given figure 
80deg = 30 deg + x 
it implies x = 50deg. 

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.

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. 

  • 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. 

ΔABC is right-angled at C. If AC = 5 cm and BC = 12 cm find the length of AB.
  • a)
    13 cm
  • b)
    11 cm
  • c)
    20 cm
  • d)
    None of these
Correct answer is option 'A'. Can you explain this answer?

By Pythagoras property,
AB2 = AC2 + BC2
= 52 + 122 = 25 + 144 = 169 = 132
or AB2= 132. So, AB = 13 or the length of AB is 13 cm.

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.

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°

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?

Shruti Baluni answered
Answer is 45 because the given triangle is isosceles , by the property of two sides of triangle are equal then the angle opposite to the sides are equal . angle 1 + angle 2 + angle 3 = 180 ( angle sum property) x + 90 + x =180 ( angle 3 = angle 2) 2x+90 =180 2x= 180 - 90 2x= 90 x = 90/2 x= 45 hence proved

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.

  • 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°

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?

Ragini jain answered
Equilateral Triangle: A Triangle with Equal Length Sides

An equilateral triangle is a specific type of triangle where all three sides are of equal lengths. It is a fundamental concept in geometry and is classified as a special case of triangles based on its side lengths.

Definition:
- An equilateral triangle is a polygon with three sides of equal lengths.
- Each internal angle of an equilateral triangle measures 60 degrees.

Key Points:
1. Equal Side Lengths: In an equilateral triangle, all three sides have the same length. This characteristic distinguishes it from other types of triangles.
2. Symmetry: Due to its equal side lengths, an equilateral triangle possesses symmetry. It can be folded along any of its medians, resulting in all three sides overlapping perfectly.
3. Regular Polygon: An equilateral triangle is the simplest form of a regular polygon. Regular polygons have all sides and angles equal.
4. Interior Angles: The interior angles of an equilateral triangle are all equal to 60 degrees. This means that when the angles are added together, they sum up to 180 degrees.
5. Exterior Angles: The exterior angles of an equilateral triangle are each equal to 120 degrees. The exterior angle is the supplementary angle to the interior angle.

Usage and Application:
- Equilateral triangles are used in various fields of study, including mathematics, art, and engineering.
- In mathematics, equilateral triangles serve as a basis for understanding geometric principles and properties.
- In art, equilateral triangles are often used to create symmetrical and balanced compositions.
- In engineering and architecture, equilateral triangles can be utilized to create stable and strong structures.

In conclusion, an equilateral triangle is a special type of triangle where all three sides are of equal lengths. It possesses symmetry, has interior angles measuring 60 degrees each, and is a fundamental concept in geometry. Understanding the properties and characteristics of an equilateral triangle is important in various fields of study and practical applications.

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 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

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

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

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 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°

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, 

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.

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

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

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°

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