PeepalTree
In the figure above, AC is a diameter of the circle. What is the area of triangle ABC?
(1) The area of the circle is \(4900\pi\) and the length of BC is 84.
(2) The perimeter of triangle ABC is 336 and the length of AB is \(\frac{4}{5}\) times the length of BC.
Since AC is the diameter of the circle, angle B = 90
(1) The area of the circle is \(4900\pi\) and the length of BC is 84.
Area of the circle will give the diameter AC, and another side BC is known. Now, since it is a right angled triangle, we can find the third side and thus the area of triangle can be found.
Sufficient
(2) The perimeter of triangle ABC is 336 and the length of AB is \(\frac{4}{5}\) times the length of BC.
The three sides are x, (4/5)x and \(\sqrt{x^2+(4/5)x^2}\) and sum of these three sides is 336x+ (4/5)x + \(\sqrt{x^2+(4/5)x^2}\) =336. we can find the value of x and thus the area.
Sufficient
D
You don't require to find the area and above would be sufficient without solving but let us solve it incase we find this in a PS question.
(1) The area of the circle is \(4900\pi\) and the length of BC is 84.
Area = \(\pi*r^2=4900\pi....r=70\), so AC =2*70=140 as it is the diameter.
Thus AB = \(\sqrt{AC^2-BC^2}=\sqrt{140^2-84^2}=\sqrt{28^2(5^2-3^2)}=28*4=112\)
Area = \(\frac{1}{2}*84*112=4704\)
(2) The perimeter of triangle ABC is 336 and the length of AB is \(\frac{4}{5}\) times the length of BC.
The three sides are x, (4/5)x and \(\sqrt{x^2+(4/5)x^2}\) and sum of these three sides is 336x+ (4/5)x + \(\sqrt{x^2+(4/5)x^2}\) =336. \(x(1+(4/5)+(3/\sqrt{5})=336\)
You can find answer but the statement I and II do not match