Final answer:
To find the perimeter of an equilateral triangle with a side length of 4.5 cm, multiply the length by 3. The perimeter is 13.5 cm, which is answer choice a).
Step-by-step explanation:
The side of an equilateral triangle is given as 4.5 cm. The perimeter of an equilateral triangle is the sum of all its sides. Since all sides are equal in an equilateral triangle, the perimeter can be found by multiplying the length of one side by 3.
The formula for the perimeter (P) of an equilateral triangle when the side length (s) is known is:
P = 3 × s
Let's apply this formula with the given side length:
P = 3 × 4.5 cm
P = 13.5 cm
Therefore, the correct answer is a) 13.5 cm.