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  5. Ratio and Proportion

6th Class Mathematics Ratio and Proportion Question Bank Ratio, Proportion & Unitary Method

  • question_answer
    The mean proportion of \[a\] and \[b\] is 10 and the value of \[a\] is four times the value of\[b\]. The value of \[a+b(a>0,\,\,b>0)\] is

    A)  20                              

    B)  25           

    C)  101                

    D)  29

    Correct Answer: B

    Solution :

    \[a:b=4:1\] Let the ratio of a and b be \[x\]and \[4x\] \[\sqrt{ab}=10\] \[ab=100\] \[x\times 4x=100\] \[4{{x}^{2}}=100\] \[{{x}^{2}}=\frac{100}{4}\] \[{{x}^{2}}=25\] \[x=25\] Then \[a=5,\text{ }b=4\times 5=20\] \[\therefore \]\[a+b=25\]


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