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(d) 3 acute angles (iv) Right-angled
(e) 1 right angle (v) Equilateral

(f) 1 obtuse angle (vi) Acute-angled
(g) 1 right angle with two sides of equal length (vii) Isosceles (NCERT)
Solution: (a) (v), (b) (vii), (c) (i), (d) (vi), (e) (iv), (f) (iii), (g) (ii)

Try It Out!
Example 19: Name each of the following triangles in
two different ways: (You may judge the What type of triangles can you construct
using
nature of the angle by observation). (a) 3 matchsticks?

(b) 4 matchsticks?
(c) 5 matchsticks?

5 cm 4 cm 17 cm 15 cm

6 cm

4 cm 6 cm
8 cm
(a) (b) (c)

10 cm 5.8 cm 5.8 cm 13 cm 8 cm

10 cm 5.8 cm 11 cm
(d) (e) (f)

Solution: (a) Acute-angled; isosceles (b) Right-angled; scalene
(c) Obtuse-angled; isosceles (d) Right-angled; isosceles
(e) Acute-angled; equilateral (f) Obtuse-angled; scalene

Types of Quadrilaterals

1. Parallelogram: A parallelogram is a quadrilateral in which
both pairs of opposite sides are parallel.

2. Rectangle: A rectangle is a parallelogram in which each
angle is a right angle.

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