The perimeter of a triangle is not greater than 12 and the lengths of sides are natural numbers. How many such kinds of triangles is it possible? Find the probability of randomly chosen triangle is isosceles but not equilateral.

3 triangles

Step-by-step explanation:

Perimeter of triangle = a + b + c

Given that :

P = 12

and a, b, c are natural numbers

Let :

Side A = a

Side B = b

Side C = 12 - (a + b)

Side A + side B > side C - - - (condition 1)

a + b > 12 - (a + b)

a + b > 12 - a - b

a + a + b + b > 12

2a + 2b > 12

2(a + b) > 12

a + b > 6

Side A - side B < side C

a - b < 12 - (a + b)

a - b + a + b < 12

2a < 12

a < 6

b < 6 (arbitrary point)

Going by the Constraint above :

The only three possibilities are :

(2, 5, 5)

(3, 4, 5)

(4, 4, 4)

Total number of triangle = 3

Equilateral triangle (all 3 sides equal) = (4, 4, 4) = 1

Isosceles triangle (only 2 sides equal) = (2, 5, 5) = 1