Find the area of a rectangle if its perimeter is 16 and one side is three times the other.

a is the width of the rectangle, b is the length of the rectangle.
The perimeter of the rectangle is:
P = 2 * (a + b).
Let b be 3 times a, then b = 3a.
16 = 2 * (a + 3a);
2 * 4a = 16;
8a = 16;
a = 16/8;
a = 2 (conventional units).
Then:
b = 3a = 3 * 2 = 6 (conventional units).
The area of the rectangle is found by the formula:
S = ab;
S = 2 * 6 = 12 (conventional square units).
Answer: S = 12 conventional square units.