If 1/a^2 + a^2 represents the diameter of circle O and 1/a + a = 5, which of the following best approximates the circumference of circle O? Choose the correct choice from the following choices.
A) 28	B) 22	C) 20	D) 16	E) 12
Given that (1/a)+a =3   Square both sides of the equation:   We get,   [(1/a)^2 + a^2 + 2*(1/a)*a] = 9   =&gt; (1/a)^2 + a^2 + 2 = 9   =&gt; (1/a)^2 + a^2 = 7 ----------------- (1)   Diameter D = (1/a)^2 + a^2   = 7 (From (1))   So Radius = D/2 = 7/2   Circumference = 2*Pi*r   = 2*(22/7)*(7/2)   =28   So the answer should be 28.
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If 1/a^2 + a^2 represents the diameter of circle O and 1/a + a = 5, which of the following best approximates the circumference of circle O?