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RD Chapter 14- Quadrilaterals Ex-14.2 Interview Questions Answers

Question 1 : Two opposite angles of a parallelogram are (3x − 2)° and (50 − x)°. Find the measure of each angle of the parallelogram.

Answer 1 : It is given that the two opposite angles of a parallelogram are   and .

We know that the opposite anglesof a parallelogram are equal.

Therefore,

 …… (i)

Thus, the given angles become

Also, 

Therefore the sum of consecutiveinterior angles must be supplementary.

That is;

Sinceopposite angles of a parallelogram are equal.

Therefore,.

And 

Hence thefour angles of the parallelogram are  and .

Question 2 : If an angle of a parallelogram is two-third of its adjacent angle, find the angles of the parallelogram.

Answer 2 :

Let one of the angle of the parallelogram as 
Then the adjacent angle becomes   
We know that the sum of adjacent angles of the parallelogram is supplementary.
Therefore,

Thus, the angle adjacent to 

Since,opposite angles of a parallelogram are equal.

Therefore,the four angles in sequence are ,,and.

Question 3 : Find the measure of all the angles of a parallelogram, if one angle is 24° less than twice the smallest angle.

Answer 3 :

Let the smallest angle of the parallelogram be  
Therefore, according to the given statement other angle becomes  .
Also, the opposite angles of a parallelogram are equal.
Therefore, the four angles become ,, and .
According to the angle sum property of a quadrilateral:

Thus, the other angle becomes

Hence,the four angles of the parallelogram are  and .

Question 4 : The perimeter of a parallelogram is 22 cm. If the longer side measures 6.5 cm what is the measure of the shorter side?

Answer 4 :

Let the shorter side of the parallelogram be  cm.
The longer side is given as cm.
Perimeter of the parallelogram is given as 22 cm
Therefore,
Hence, the measure of the shorter side is cm.

Question 5 : In a parallelogram ABCD, ∠D  = 135°, determine the measures of ∠A and ∠B.

Answer 5 :

It is given that ABCD is a parallelogram with  
We know that the opposite angles of the parallelogram are equal.
Therefore,
Also,  and  are adjacent angles, which must be supplementary.
Therefore,
Hence ,   and  .

Question 6 : ABCD is a parallelogram in which ∠A = 70°. Compute ∠B, ∠C and ∠D.

Answer 6 :

It is given that ABCD is a parallelogram with   
 
We know that the opposite angles of the parallelogram are equal.
Therefore,
Also,  and  are adjacent angles, which must be supplementary.
Therefore,
Also,  and  are opposite angles of a parallelogram.
Therefore,
 
Hence, the angles of a parallelogram are  ,  ,   and   .

Question 7 : In the given figure, ABCD is a parallelogram in which ∠A = 60°. If the bisectors of ∠A and ∠B meet at P, prove that AD = DP, PC = BC and DC = 2AD.

Answer 7 :

The figure is given as follows:
 
It is given that ABCD is a parallelogram.
Thus,
 
Opposite angles of a parallelogram are equal.
Therefore,  
Also, we have AP as the bisector of  
Therefore,
  …… (i)
Similarly,
  …… (ii)
We have  ,
 
From (i)
 
Thus, sides opposite to equal angles are equal.
Similarly, 
 
From (ii)
 
Thus, sides opposite to equal angles are equal.
 
Also,

Question 8 : In the given figure, ABCD is a parallelogram in which ∠DAB = 75° and ∠DBC = 60°. Compute ∠CDB and ∠ADB.

Answer 8 :

The figure is given as follows:
 
It is given that ABCD is a parallelogram.
Thus  
And  are  alternate interior opposite angles.
Therefore,
 
  …… (i)
We know that the opposite angles of a parallelogram are equal. Therefore,
Also, we have  
Therefore,
  …… (ii)
In  
By angle sum property of a triangle.
 
From (i) and (ii),we get:
 
Hence, the required value for   is  
And   is  .

Question 9 : In the given figure, ABCD is a parallelogram and E is the mid-point of side BC. If DE and AB when produced meet at F, prove that AF = 2AB.

Answer 9 :

Figure is given as follows:
 
It is given that ABCD is a parallelogram.
 
DE and AB when produced meet at F.
We need to prove that  
It is given that  
Thus, the alternate interior opposite angles must be equal.
In   and  , we have
  (Proved above)
  (Given)
  (Vertically opposite angles)
Therefore,
  (By ASA Congruency )
By corresponding parts of congruent triangles property, we get
DC = BF …… (i)
It is given that ABCD is a parallelogram. Thus, the opposite sides should be equal. Therefore,
  …… (ii)
But,
 
From (i), we get:
 
From (ii), we get:
 
Hence proved.

Question 10 :
Which of the following statements are true (T) and which are false (F)?

(i) In a parallelogram, the diagonals are equal.
(ii) In a parallelogram, the diagonals bisect each other.
(iii) In a parallelogram, the diagonals intersect each other at right angles.
(iv) In any quadrilateral, if a pair of opposite sides is equal, it is a parallelogram.
(v) If all the angles of a quadrilateral are equal, it is a parallelogram.
(vi) If three sides of a quadrilateral are equal, it is a parallelogram.
(vii) If three angles of a quadrilateral are equal, it is a parallelogram.
(viii) If all the sides of a quadrilateral are equal it is a parallelogram.

Answer 10 :

(i) Statement: In a parallelogram, the diagonals are equal.
False
(ii) Statement: In a parallelogram, the diagonals bisect each other.
True
(iii) Statement: In a parallelogram, the diagonals intersect each other at right angles.
False
(iv) Statement: In any quadrilateral, if a pair of opposite sides is equal, it is a parallelogram.
False
(v) Statement: If all the angles of a quadrilateral are equal, then it is a parallelogram.
True
(vi) Statement: If three sides of a quadrilateral are equal, then it is not necessarily a parallelogram.
False
(vii) Statement: If three angles of a quadrilateral are equal, then it is no necessarily a parallelogram.
False
(viii) Statement: If all sides of a quadrilateral are equal, then it is a parallelogram.
True


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