AbdurRakib wrote:

A fish tank contains orange fish and silver fish. After k more orange fish and 2k more silver fish are added, the probability of choosing an orange fish at random is \(\frac{1}{3}\) . What was the probability of choosing a silver fish before any more fish were added?

(A) \(\frac{1}{4}\)

(B) \(\frac{1}{3}\)

(C) \(\frac{1}{2}\)

(D) \(\frac{2}{3}\)

(E) \(\frac{3}{4}\)

Equation (1): \(o + k = 1x\)

Equation (2): \(s + 2k = 2x\)

Multiplying the first Equation by 2: \(2o + 2k = 2x\). Let´s call this last equation, Equation (3): \(2o + 2k = 2x\)

We can subtract Eq (3) \(-\) Eq (2): \(2o - s = 0\), and then \(s = 2o\).

Then, \(\frac{s}{s+o} = \frac{2o}{3o} = \frac{2}{3}\).

The correct answer is letter

(D).

_________________

Prof Marcelo Roseira

Curso FDX

GMAT Prep Online

Brazil

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