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NCERT Exemplar · Class 9 · Maths

Chapter 11: Constructions

Practice each question, then open the answer or worked solution.

Exercise 11.1

Textbook page 109 · 1 questions
Q1Written answer

With the help of a ruler and a compass, it is not possible to construct an angle of :

(A) 37.5°

(B) 40°

(C) 22.5°

(D) 67.5°

Show solutionHide solution
Worked solution

(B) 40°

Explanation:

Considering Option (A):

37.5° = ½ × 75°

75° can be constructed with the help of a ruler and a compass.

Considering Option (B):

40° = ½ × 20°

This is not possible.

20° cannot be constructed with the help of a ruler and a compass.

Considering Option (C):

22.5° = ½ × 45°

45° can be constructed with the help of a ruler and a compass.

Considering Option (D):

67.5° = 1/2 × 135° = 1/2 × (90° + 45°)

Both 90° and 45° can be constructed with the help of a ruler and a compass.

Hence, option (B), is not possible to construct an angle of 40° with the help of a ruler and compass is the correct answer.