Plug the known variables into the equation.
p=2l+2w
200=2l+2(30)
200=2l+60
140=2l
l=70
The answer is C. 70mm.
Observe that
y = x² - 2kx = x (x - 2k)
has roots at x = 0 and x = 2k. Since the leading coefficient is 1 > 0, the parabola opens upward, and in particular this means the x-axis lies above the curve.
We can compute the area of R by integrating:

Solve for k :

Answer:
D. allows a person to borrow more money at a lower interest rate
The area of the rectangular pen is 10,000 m² and the area of the circular pen is 12,738.95 m².
For the rectangular pen, we want the sides to be congruent. To minimize perimeter and maximize area, the figure needs to be equilateral.
400/4 = 100 m for each side
This means that the area is 100(100) = 10,000 m².
If the pen is circular, this means the circumference is 400 m. Circumference is given by the formula C=πd:
400 = 3.14d
Divide both sides by 3.14:
400/3.14 = 3.14d/3.14
127.389 = d
The radius is half of the diameter:
r = 127.389/2 = 63.6945
The area of the circle is given by A=πr²:
A=3.14(63.6945)² = 12738.9465 ≈ 12738.95 m²