Ncert -Class 7- Maths -worksheet – Line and Angles

PROBLEMS

Question :

In a Δ ABC ∠A= 35º and ∠B= 65º ,  find the measure of ∠C

Solution:

We know that the sum of the angles of a triangle is 180º

Hence, the measure of ∠C = 80º

Question :

Find the angles of a triangle which are in the ratio 3 : 4 : 5

Solution:

Let the measures of the given angles of the triangle be 3x+4x+5x=180º

12x=180

x=15

So, the angles of the triangle are 45º , 60º, 75º ,

Question

Two angles of a triangle are equal and the third angle measures . Find the measure of each of the unknown angles.

Solution:

Let the measure of each unknown angle be
We know that the sum of the angles of a triangle is 180º

x+x+70=180

=> 2x-110

=>x =55

Question

The adjoining figure has been obtained by using two triangles

Prove that ∠A +∠B+∠C+∠D+∠E+∠F=360º

Question

One side of a triangle is produced and the exterior angle so formed is 120º. If the interior opposite angles be in the ratio 3:5, find the measure of each angle of the triangle.

Single choice Question

1.The sum of an angle and one third of its supplementary angle is 90°. What is the measure of the angle?

a) 120°                      b) 60°
c) 135°                      d) 45°

2. An angle is thrice of it’s supplement, what is the measure of the angle?

a) 120°                      b) 60°
c) 135°                      d) 45°

3. Two complementary angles are in the ratio 2 : 3. What is the measure of the small angle?

a) 36°                      b) 60°
c) 46°                      d) 45°

4. The sum of an angle and half of it’s complimentary angle is 75°. Find the measure of the angle.

a) 120°                      b) 60°
c) 135°                      d) 45°

5. Two supplementary angles are in 2 : 7 ratio, find the larger angle.

a) 120°                      b) 60°
c) 140°                      d) 40°

Fill in the blanks

a)Two ______________ are said to form linear pair of the angels if their non common arms are two opposite rays.
b) if a ray stands on a line then the sum of the adjacent angles so formed is _______________.
c) The sum of all angles around a point is _________________.
d) An angle which is equal to its complement is _____________.
e) Two angles are called a pair of _____________________ if their arms form two pairs of opposite rays.
f) If two lines intersect then the Vertically opposite angles are  _____________
g) A line which intersects two or more lines at distinct points is called a ___________________
h) You can draw _____________ transversals on a line.
(i) If  two lines are intersected by a transversal such that any pair of corresponding angles are equal then the lines are _________________