Answer: 15x15
Explanation:
I'm assuming this is an optimization problem in a Calculus class, if not just disregard all of this and be happy with the answer.
We can write two equations for the value of x and y lengths of this rectangle.
2y+2x=60
xy=A
Solve our perimeter equation for y, y=30-x.
This gives us x(30-x)=A, and 30x-x²=A.
Find the derivative of the area function: A'=30-2x
To maximize we set A' to 0: 0=30-2x, x=15
Plug back into our perimeter formula: 2y+2(15)=60, y=15
So both sides will be 15 inches.