8th Class Mathematics Rational Numbers Question Bank Rational Numbers

  • question_answer
    Arrange \[\frac{-4}{5},\frac{9}{-15}\] and \[\frac{-2}{3}\] in descending order.

    A)  \[\frac{9}{-15},\frac{-2}{3},\frac{-4}{5}\]

    B)                         \[\frac{-2}{3},\frac{-4}{5},\frac{-9}{15}\]

    C)                         \[\frac{9}{-15},\frac{-4}{5},\frac{-2}{3}\]

    D)                         \[\frac{-2}{3},\frac{-9}{15},\frac{-4}{5}\]

    Correct Answer: A

    Solution :

    Writing each rational number with a positive denominator, we have \[\frac{-4}{5},\frac{-9}{15}\]  and \[\frac{-2}{3}\]. L.C.M of 5, 15 and 3 is 15. \[\therefore \]  \[\frac{-4}{5}=\frac{(-4)\times 3}{5\times 3}=\frac{-12}{15}\]                 \[\frac{-2}{3}=\frac{(-2)\times 5}{3\times 5}=\frac{-10}{15}\] Since \[-12<-10<-9,\] we have \[\frac{-12}{15}<\frac{-10}{15}<\frac{-9}{15}\Rightarrow \frac{-4}{5}<\frac{-2}{3}<\frac{-9}{15}\] \[\Rightarrow \]    \[\frac{-9}{15}>\frac{-2}{3}>\frac{-4}{5}\].


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