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Suppose x varies inversely as y, y varies directly as the sq...

Suppose x varies inversely as y, y varies directly as the square of t and x = 1, when t = 3. Find x when t = 13.

A.

81

B.

27

C.

19

D.

127

E.

181

Correct answer is A

x1y

x=ky

yt2

y=ct2 

k and c are constants.

x=kct2

Let kc=d (a constant)

x=dt2

1=d32d=9

x = 9 \div (\frac{1}{3})^{2}

= 9 \div \frac{1}{9} = 9 \times 9 = 81