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SSC Quantitative Aptitude Average Question Bank Average (I)

  • question_answer
    In a class with a certain number of students, if one student weighing 50 kg is added, then the average weight of the class increases by 1 kg. If one more student weighing 50 kg is added, then the average weight of the class increases by 1.5 kg over the original average. What is the original average weight of the class?

    A) 2 kg

    B) 4 kg

    C) 46 kg

    D) 47 kg

    Correct Answer: D

    Solution :

    [d] Let the number of students be x and average weight be y kg. Then,    \[\frac{xy+50}{(x+1)}=(y+1)\] \[\Rightarrow \]   \[xy+50=xy+x+y+1\] \[\Rightarrow \]   \[x+y=49\]                                …(i)             \[\frac{xy+50+50}{(x+2)}=\left( y+\frac{3}{2} \right)\] \[\Rightarrow \]   \[xy+100=xy+\frac{3}{2}x+2y+3\] \[\Rightarrow \]   \[\frac{3}{2}x+2y=97\] \[\Rightarrow \]   \[3x+4y=194\]                          …(ii) Multiplying Eq. (i) by 3 and subtracting it from Eq. (ii), we get \[y=47\] \[\therefore \] Original average weight of the class is 47 kg.


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