8th Class Mathematics Direct and Inverse Proportions Question Bank Direct and Inverse Proportions

  • question_answer If A : B = 1: 3 and B : C = 4 : 5, then C : A is equal to __.

    A)  15 : 8             

    B)  12 ; 10

    C)  8 : 5   

    D)         8 : 15

    Correct Answer: A

    Solution :

    \[\frac{A}{B}=\frac{2}{3}\Rightarrow B=\frac{3}{2}A\]               ?(i) Also, \[B:C=4:5\] or \[\frac{B}{C}=\frac{4}{5}\] \[\Rightarrow \frac{\frac{3}{2}A}{C}=\frac{4}{5}\] or \[\frac{3A}{2C}=\frac{4}{5}[from\,\,(i)]\] \[\Rightarrow \frac{A}{C}=\frac{4\times 2}{5\times 3}\Rightarrow \frac{A}{C}=\frac{8}{15}\Rightarrow C:A=15:8\]

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