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      Question

      The average of four numbers (z+16), (y+15), (y-25) and

      1.2z is (y-6). If one more number which is 144 is added then the new average will be (y-1). The value of ‘z’ is what percentage of the value of ‘y’?
      A 60% Correct Answer Incorrect Answer
      B 80% Correct Answer Incorrect Answer
      C 75% Correct Answer Incorrect Answer
      D 90% Correct Answer Incorrect Answer
      E None of the above Correct Answer Incorrect Answer

      Solution

      The average of four numbers (z+16), (y+15), (y-25) and 1.2z is (y-6).

      (z+16)+(y+15)+(y-25)+1.2z = 4(y-6)    Eq.(i)

      If one more number which is 144 is added then the new average will be (y-1).

      (z+16)+(y+15)+(y-25)+1.2z+144 = 5(y-1)

      Put Eq.(i) in the above equation.

      4(y-6)+144 = 5(y-1)

      4y-24+144 = 5y-5

      5y-4y = 144-24+5

      y = 125

      Put the value of ‘y’ in Eq.(i).

      (z+16)+(125+15)+(125-25)+1.2z = 4(125-6)

      (z+16)+140+100+1.2z = 4x119

      (z+16)+140+100+1.2z = 476

      256+2.2z = 476

      2.2z = 476-256 = 220

      z = 100

      Required percentage = (100/125)x100

      = (4/5)x100

      = 80%

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