Question 1:
Name the types of following triangles:
(a) Triangle with lengths of sides 7 cm, 8 cm and 9 cm.
(b) ΔABC with AB = 8.7 cm, AC = 7 cm and BC = 6 cm.
(c) ΔPQR such that PQ = QR = PR = 5 cm.
(d) ΔDEF with m∠D = 90°
(e) ΔXYZ with m∠Y = 90° and XY = YZ.
(f) ΔLMN with m∠L = 30°, m∠M = 70° and m∠N = 80°
Answer:
(a) Scalene triangle
(b) Scalene triangle
(c) Equilateral triangle
(d) Right-angled triangle
(e) Right-angled isosceles triangle
(f) Acute-angled triangle
Question 2:
Match the following:
Measures of Triangle |
Type of Triangle |
(i) 3 sides of equal length |
(a) Scalene |
(ii) 2 sides of equal length |
(b) Isosceles right angled |
(iii) All sides are of different length |
(c) Obtuse angled |
(iv) 3 acute angles |
(d) Right angled |
(v) 1 right angle |
(e) Equilateral |
(vi) 1 obtuse angle |
(f) Acute angled |
(vii) 1 right angle with two sides of equal length |
(g) Isosceles |
Answer:
(i) Equilateral (e)
(ii) Isosceles (g)
(iii) Scalene (a)
(iv) Acute-angled (f)
(v) Right-angled (d)
(vi) Obtuse-angled (c)
(vii) Isosceles right-angled (b)
Question 3:
Name each of the following triangles in two different ways: (you may judge the nature of the angle by observation)
Answer:
(a) Acute-angled and isosceles
(b) Right-angled and scalene
(c) Obtuse-angled and isosceles
(d) Right-angled and isosceles
(e) Acute-angled and equilateral
(f) Obtuse-angled and scalene
Question 4:
Try to construct triangles using match sticks. Some are shown here. Can you make a triangle with
(a) 3 matchsticks?
(b) 4 matchsticks?
(c) 5 matchsticks?
(d)6 matchsticks?
(Remember you have to use all the available matchsticks in each case)
Name the type of triangle in each case. If you cannot make a triangle, think of reasons for it.
Answer:
(a) By using 3 matchsticks, we can form a triangle as
(b) By using 4 matchsticks, we cannot form a triangle. This is because the sum of the lengths of any two sides of a triangle is always greater than the length of the remaining side of the triangle.
(c) By using 5 matchsticks, we can form a triangle as
(d) By using 6 matchsticks, we can form a triangle as