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A fraction is such that if the numerator is multiplied by 2 and the denominator is reduced by 4 we get \(\frac{10}{3}\), but if the numerator is increased by 6 and the denominator is doubled we get \(\frac{11}{14}\), what is the fraction?

  • A.\(\frac{7}{5}\)
  • B.\(\frac{5}{7}\)
  • C.\(\frac{21}{17}\)
  • D.\(\frac{17}{21}\)

Answer: B

The fraction is \(\frac{5}{7}\).

Let the fraction be \(\frac{x}{y}\). The two conditions give

\[ \begin{aligned} \frac{2x}{y - 4} = \frac{10}{3} &\Rightarrow 6x = 10y - 40 \\ \frac{x + 6}{2y} = \frac{11}{14} &\Rightarrow 14x + 84 = 22y \end{aligned} \]

From the first, \(x = \frac{5y - 20}{3}\). Substituting in the second and multiplying through by 3 gives \(70y - 280 + 252 = 66y\), so \(4y = 28\), \(y = 7\) and \(x = 5\).

Check: \(\frac{10}{3}\) and \(\frac{11}{14}\) both come out. \(\frac{7}{5}\) is the reciprocal, and the other options fail the first condition.

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