The perimeter of the triangle is 12cm 4mm. The length of one side is 4cm 9mm, the other is 3cm 7mm.

The perimeter of the triangle is 12cm 4mm. The length of one side is 4cm 9mm, the other is 3cm 7mm. Find the length of the third side.

The perimeter of a triangle is 12 centimeters 4 millimeters.
The first side is 4 centimeters 9 millimeters long.
The length of the second side is 3 centimeters 7 millimeters.

Let’s translate everything into millimeters:
1 cm = 10 mm.
12 cm 4 mm = 124 mm.
4 cm 9 mm = 49 mm.
3 cm 7 mm = 37 mm.

Let’s calculate the length of the third side of the figure:
124 – 49 – 37 = 75 – 37 = 38 millimeters or 3 centimeters 8 millimeters.
Answer: the third side of the triangle is 3 centimeters 8 millimeters.