Saturday 16 February 2013

8th Polygons Solved Questions Paper[CBSE Maths]

1.Q. Find the number of diagonals in an octagon?

Ans: Number Of Diagonals Of Polygon = n(n-3) / 2     
Where n is Number Of Sides
Here n = 8
Diagonals= [8(8-3)5]/2 = 20
2.Q. Find the number of sides of a polygon whose each exterior angle is 450 .

Ans: Measure of Each Exterior Angle of a Polygon = 360/n
Each Exterior Angle = 45
45 = 360/n
Number of Sides = 360/45 =8
So Number of Sides = 8
3. Q. The sum of the interior angles of a regular polygon is 3 times the sum of its exterior angles. Determine the number of sides of the polygon.

Ans: sum of the interior angles of a regular polygon is 3 times the sum of its exterior angles.
We know that in a regular polygon sum of all the exterior angles = 360°
Therefore, sum of interior angles = 3 × 360° = 1080°
Again, we have sum of interior angles, S = (n - 2)180°, where n is the number of sides of the polygon
⇒ (n - 2)180° = 1080°
⇒ n - 2 = 6
⇒ n = 8

4. Q.  (a) What is the minimum interior angle possible for a regular polygon? Why?

 (b) What is the maximum exterior angle possible for a regular polygon?

Answer: The polygon with minimum number of sides is a triangle, and each angle of an equilateral triangle measures 60°, so 60° is the minimum value of the possible interior angle for a regular polygon. For an equilateral triangle the exterior angle is 180°-60°=120° and this is the maximum possible value of an exterior angle for a regular polygon.
The sum of the exterior angles of any polygon= 3600

Hence, the polygon of 8 sides is octagon.


5. Q. Find the measure of each exterior angle of a regular polygon of 9 sides.

Ans: Total measure of all exterior angles = 360
No. of sides = 9
Measure of each exterior angle = 360/9 = 40

6.Q. If the sum of the measures of the interior angles of a polygon equals the sum of the measures of the exterior angles, how many sides does the polygon have?


Ans:The sum of the measures of the interior angles of a polygon with n sides =(n-2)x1800
(n-2) x1800 = 3600            Þ      n=2+2=4
7.Q. The sum of the interior angles of a regular polygon is:(n - 2) × 180° where n is the number of sides of the polygon.

Solution: The sum of its exterior angles of regular polygon= 360°
The exterior angle of a regular polygon
Interior angle of a regular polygon = sum of interior angles ÷ number of sides
8. Q.What is the measure of the each angle of regular Hexagon?

Ans: No. of sides in regular hexagon = 6
The measure of the each angle =[(2n – 4)x900 /n ]=[2x6-4]x900/6 =7200 /6 =1200
9. Q. Find the number of sides of a polygon whose each interior angle is 1560 .

Ans each exterior angle = 180 - 1560 = 240
Measure of Each Exterior Angle of a Polygon = 360/n
 Þ 24= 360/n       Þ n = 360/24 =15
10.Q.  Two regular polygons are such that the ratio between their no. of sides is 1:2 and the ratio of measures of their interior angle is 3:4. Find the number of sides of each polygon.

Ans: let the number of sides are x and 2x
then their interior angles will be [{(2n-4)/n}x900]       and [{(4n-4)/n}x900]
A/Q, the ratio of measures of their interior angle = 3:4
Þ [{(2n-4)/n}x900] ¸ [{(4n-4)/n}x900] = ¾
On solving this we get , n=5
So, the numbers of sides are 5 and 2x5=10

8th Polygons Solved Questions Paper  Download File

8 comments:

  1. Thank you for sharing this post as I am searching for this for over a long time as my brother looking for 8th Polygons Solved Questions Paper[CBSE Maths] from the long time!!! Thank you once again posting the Solved Question papers.

    ReplyDelete
  2. Thank you very much for posting these important question.

    ReplyDelete
  3. Very Helpful Post. Keep sharing such informative articles.
    CBSE curriculum school in ajman

    ReplyDelete
  4. Nice idea!! Thank you so much for such information. I’ve been waiting patiently for your next blog entry!
    List of Best Schools in Dubai

    ReplyDelete
  5. Excellent questions very good for doubt clearing

    ReplyDelete
  6. These are really good questions. Thank you so much!

    ReplyDelete