Understanding Quadrilaterals – Class 8.
Chapter 3 of NCERT/CBSE Class 8 Mathematics is about Understanding Quadrilaterals. Here in this lesson you can find out practice problems from this chapter.
CBSE CLASS 8 MATHEMATICS
Understanding Quadrilaterals – Chapter 3 / Model Questions.
Fill in the blanks:
- A 10 sided polygon is known as ————-
- A line segment connecting two non-consecutive vertices of a polygon is called ———-
- The name of a regular polygon with 4 sides is ———–
- The number of diagonals a regular hexagon have ————
Answer the following:
- In a parallelogram ABCD, opposite sides are given by 4x – 4 and x -1. Find the value of x?
- Find the sum of all the exterior angles of a triangle?
- In a triangle PQR, the three angles are given by (x + 5), (x + 10) and (3x + 15). Find the value of x?
- Three angles of a quadrilateral are 35, 65 and 128 degrees. Find the measure of the fourth angle?
- In a parallelogram ABCD, if one angle is 70 degree, find all the other angles?
- Find the perimeter of a parallelogram whose sides are given by 6 cm and 12 cm?
- Square or Rhombus
- 9 sides
- Since the opposite sides of a parallelogram are of equal measure,
4x – 4 = x – 1
4x – x = -1 + 4
3x = 3
x = 1.
- We know that the sum of the measures of the external angles of any polygon is 360 degree. Therefore, sum of all the exterior angles of a triangle is 360 degree.
- By angle sum property of triangles, sum of the three angles = 180 degree
x + 5 + x + 10 + 3x + 15 = 180
5x + 30 = 180
5x = 180 – 30 = 150
x = 150 / 5 = 30
- We know that sum of four angles of a quadrilateral is 360 degree.
Let the fourth angle be x and the other three angles are 35, 65 and 128.
Therefore, 35 + 65 + 128 + x = 360
228 + x = 360
x = 132
Therefore, the measure of fourth angle is 132 degree.
- Since the opposite angles of a parallelogram are equal, the measures of 2 angles are 70 degree. Also adjacent angles of a parallelogram are supplementary. Therefore, the other two angles are 110 degree each.
- In a parallelogram the opposite sides have same length.
So perimeter = 6 + 12 + 6 + 12 = 36 cm