Page 56 - Ganit Kaushal

Subjective/Competency Based Questions

Ex 19. Find out the number of acute angles in each of the figures below. (NCERT)
What will be the next figure, and how many acute angles will it have?

Do you notice any pattern in the numbers? Explain it.
Sol. The number of acute angles in the given figures are 3, 12
and 21, respectively.
The pattern followed here is that every next term is obtained by adding 9 to the
previous term. So, the next figure must contain 30 acute angles.
The adjoining figure is going to be the next figure in this pattern.
Ex 20. In the adjoining figure, write the measures of the
following angles: (NCERT)

(a) ∠KAL (b) ∠WAL
(c) ∠TAK
Sol. Observing the long marks covered by each
of the following angles, we conclude that:
(a) ∠KAL = 30° (b) ∠WAL = 50°

(c) ∠TAK = 120°
Ex 21. Find the degree measures of the following angles using a protractor. (NCERT)

Sol. 45°, 25°, 110°, respectively, from left to right.
Ex 22. How can you find the degree measure of the angle ‘y’ given in the adjoining figure,
using a protractor? (NCERT)
Sol. We have ∠x + ∠y = 360°
∴ ∠y = 360° – ∠x

Using a protractor, we find that ∠x = 100°
\ ∠y = 360° – 100° = 260°
Ex 23. Find the degree measures of ∠BXE, ∠CXE,
∠AXB, and ∠BXC in the figure given.
(NCERT)
Sol. Observing the long marks and medium-sized
marks covered by each angles. We conclude that

∠BXE = 115°
∠CXE = 85°
∠AXB = 65°
∠BXC = 30°

54 Mathematics-6