The 2 sides of the triangle are, respectively, 8 and 9 m in 5 cm and 1 m 3 cm.

The 2 sides of the triangle are, respectively, 8 and 9 m in 5 cm and 1 m 3 cm. Find its third side if the perimeter of the triangle is 2 m 60 cm.

1) a = 8 dm 5 cm = 0.85 m, b = 1 m 3 cm, P = 2 m 60 cm (by condition);

2) P = a + b + c (known formula);

3) c = P – (a + b);

4) c = 2.6 – (0.85 + 1.3) = 2.6 – 2.15 = 0.45 m = 4 dm 5 cm.

Answer: 4 dm 5 cm.

Explanation: The perimeter of a triangle is the sum of the lengths of all its sides. Since we know the two sides and the perimeter, substituting the values into the formula, we can find the third side.