Bunuel
Official Solution:
This is a 700+ question.
(1) \(a-b=15\). Must know for the GMAT: the length of any side of a triangle must be larger than the positive difference of the other two sides, but smaller than the sum of the other two sides. So, \(a+b \gt c \gt 15\), which means that \(a+b+c \gt 30\). Sufficient.
(2) The area of the triangle is 50. For a given perimeter equilateral triangle has the largest area. Now, if the perimeter were equal to 30 then it would have the largest area if it were equilateral. Let's find what this area would be: \(Area_{equilateral}=s^2*\frac{\sqrt{3}}{4}=(\frac{30}{3})^2*\frac{\sqrt{3}}{4}=25*\sqrt{3} \lt 50\). Since even an equilateral triangle with perimeter of 30 cannot produce the area of 50, then the perimeter must be more than 30. Sufficient.
Answer: D
HI,
I understood Statement 1 is sufficient.
However, I have issues understanding statement 2.
How can we confirm that "For a given perimeter equilateral triangle has the largest area.".
Can it be proved by a theorem?
Thanks