# Lines and Angles – Class 9/Maths.

**Chapter 6 of NCERT/CBSE Class 9 Maths is about Lines and Angles. Here you can find out practice problems for this chapter.**

**CBSE CLASS 9 MATHEMATICSLines and Angles – Chapter 6 /Sample Papers.Fill in the blanks:**

- An angle whose measure is less than 90 degree is called an ————-
- An angle whose measure is more than 90 degree is called an————–
- An angle whose measure is 90 degree is called a ——-
- The measure of a straight angle is ————degree.
- An angle whose measure is 360 degree is called a ————–
- An angle whose measure is more than 180 degree but less than 360 degree is called ——-
- Two angles whose sum is 90 degree are called —————–
- Two angles whose sum is 180 degree are called ————-
- If three or more points lie on the same line, they are called —————
- When the sum of two adjacent angles is 180 degree, then they are called a ————–of angles.
**Answer the following questions:** - Find the supplement of ¾ of 120 degree.
- If (2x – 35) and (x + 5) are complementary angles, find the angles.
- Two supplementary angles are in the ratio 1:2, find the angles.
- If a transversal intersects two parallel lines, then

i) each pair of ———— angles is equal

ii) each pair of ———- angles is equal

iii) each pair of interior angles on the same side of the transversal is ————– - If the angles of a triangle are in the ratio 1:2:3, then find the measures of the three angles?

**ANSWERS:**

- Acute angle
- Obtuse angle
- Right angle
- 180
- Complete angle
- Reflex
- Complementary
- Supplementary
- Collinear points
- Linear pair
- ¾ of 120 = ¾ x 120 = 90 degree

Supplement of 90 degree is 90 degree itself. - Given (2x – 35) and (x + 5) are complementary angles. So their sum must be 90 degree.

2x – 35 + x + 5 = 90

3x – 30 = 90

3x = 90 + 30

3x = 120

x = 120/3 = 40

So the angles are 2x -35 = 2 x 40 –35 = 80 – 35 = 45 degree

x + 5 = 40 + 5 = 45 degree. - Let the angles be x and 2x

Since it is supplementary, their sum must be 180 degree.

Therefore, x + 2x = 180

3x = 180

x = 180/3 = 60

So the two angles are 60 degree and 120 degree. - i) corresponding angles

ii) Alternate interior angles

iii) Supplementary - Let the three angles be x, 2x and 3x.

By Angle sum property of triangles, x + 2x + 3x = 180

6x = 180

x= 180/6 = 30 degree

So the three angles are 30, 60 and 90 degrees.