Geometry

Question Analysis:
This question tests the perimeter formula of an equilateral triangle.

Key Concept Explanation:
The perimeter of an equilateral triangle is: P = 3s, where s is the length of one side.

Step-by-Step Solution:
Given one side is 7 cm, apply the formula: P = 3(7) = 21
The perimeter is 21 cm, making the statement true.

Common Mistakes:
Forgetting that th...