SSC Sample Paper Mock Test-13 SSC CGL Tear-II Paper-1

  • question_answer
    If ?b? is the mean proportional of 'a' and 'c', then\[{{(a-b)}^{3}}:{{(b-c)}^{3}}\] is equal to

    A)  \[a:b\]  

    B)  \[{{a}^{2}}:{{b}^{2}}\]

    C)  \[{{a}^{3}}:{{b}^{3}}\]

    D)  \[{{a}^{3}}:{{c}^{3}}\]

    Correct Answer: C

    Solution :

    By question, b is the mean-proportional of a and c. So,       \[\frac{a}{b}=\frac{b}{c}=k\]                (let say); \[\therefore \]      \[a=bk\] and \[b=ck\] \[\therefore \]      \[\frac{{{(a-b)}^{3}}}{{{(b-c)}^{3}}}=\frac{{{(bk-b)}^{3}}}{{{(ck-c)}^{3}}}\] \[=\frac{{{b}^{3}}{{(k-1)}^{3}}}{{{c}^{3}}{{(k-1)}^{3}}}=\frac{{{b}^{3}}}{{{c}^{3}}}=\frac{{{a}^{3}}}{{{b}^{3}}}\]


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