The average weight of X, Y and Z is 74 kg. If the average weight of X and Y be 68 kg and that of Y and Z be 78 kg, then the weight (in kg) of Y is
Given that average value of x & y is 68kg
$$\frac{x+y}{2}= 68$$
$$x+y=68\times2=136$$.......(1)
also,
$$\frac{z+y}{2}= 78$$
$$x+y=78\times2=156$$...(2)
average of x,y& z is 74kg
$$\frac{x+y+z}{3}= 74$$
$$x+y+z=74\times3=222$$.......(3)
subtracting eq. 3 from sum of eq. 1 & 2Â
$$292\ -\ 222=70$$
Hence, option B is right answer.
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