In an isosceles triangle, the side is 3 cm and the base is 3 cm more to find the perimeter.

1. Since the perimeter of a triangle is equal to the sum of the lengths of all its sides, we first find the length of each side of this triangle.

2. It is known that this triangle is isosceles; the lengths of its lateral sides are equal.

3. According to the condition of the problem, the length of the lateral side of the triangle is 3 cm, and the length of the base is 3 cm longer. This means that the length of the base of an isosceles triangle is 3 + 3 = 6 cm.

4. So, given an isosceles triangle with side lengths of 3 cm, 3 cm and 6 cm.

5. The perimeter of this triangle is 3 + 3 + 6 = 12 cm.

Answer: the perimeter of the triangle is 12 cm.