The perimeter of a triangle is 640mm. Find the length of the third side if it is known that the

The perimeter of a triangle is 640mm. Find the length of the third side if it is known that the two sides of this triangle are equal by 2dm4cm.

Condition:

P = 640 mm,

a = b = 2dm 4cm

c =? mm.

Solution:

2 dm 4 cm = 200 mm + 40 mm = 240 mm.

The perimeter of a triangle is equal to the sum of the lengths of its sides:

P = a + b + c, where a, b and c are the sides of the triangle.

Let s = x mm, then

240 + 240 + x = 640;

480 + x = 640;

x = 640 – 480;

x = 160.

c = 160 mm = 16 cm.

Answer: 16 cm perimeter of the triangle.