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7th Class Mathematics Simple Equations Question Bank Simple Equations

  • question_answer
    Given \[\frac{1}{u}+\frac{1}{v}=\frac{1}{f},\] find the value of 'v' when \[f=20\] and \[u=30\].

    A)  \[-20\]                

    B)         \[-60\]

    C)  \[60\]                                    

    D)  \[-30\]

    Correct Answer: C

    Solution :

      \[\frac{1}{u}+\frac{1}{v}=\frac{1}{f}\] \[\Rightarrow \] \[\frac{1}{v}=\frac{1}{20}-\frac{1}{30}=\frac{3-2}{60}=\frac{1}{60}\] \[\Rightarrow \] \[v=60\]


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