Each side of an equilateral triangle expands at the rate of 2 cm/sec. The rate of increase of its area when each side is 10 cm is (in cm2/sec).
Answer & explanation
Correct answer: option 2
$\frac{dy}{dx}=2cm\sec$, x = 10cm
$A=\frac{\sqrt{3}}{4}x^2⇒\frac{dA}{dt}=\frac{\sqrt{3}}{2}x\frac{dx}{dt}=\frac{\sqrt{3}}{2}(10)(2)=10\sqrt{3}$ sq cm/sec.