Answer: the length of the prism is 9cm
Step-by-step explanation:
The formula for determining the volume of a rectangular prism is expressed as
Volume = length × height × width
Volume = LWH
The length of the rectangular prism is three times the width.. It means that
L = 3W
The height and the width are the same. This means that
H = W
Therefore,
Volume = 3W × × W × W = 3W³
If the volume of the prism is 81 cubic centimeters, it means that
81 = 3W³
Dividing through by 3, it becomes
81/3 = 3W³/3
W³ = 27
Taking cube root of both sides, it becomes
W = 3
Therefore, the the length of the prism would be
L = 3W = 3 × 3
L = 9 cm