The average age of 10 members of the board of directors of a company is the same as it was 4 years ago, because an old member has been replaced by a young member. Find how much younger is the new member?

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4 years back: Let the sum of nine directors (total) =x The age of the old director who was replaced=z The board’s average 4 yrs before=(x+z)/10.

Present time: After 4 yrs let z be replaced by y. So now the average age of the board is=(x+4*9+y)/10 Now (x+z)/10=(x+36+y)/10 So after solving it found z=y+36. z-y=36

Now this gives us the difference between the Old person’s age four years back and the younger member’s current age. Their difference will be (z+4)-y= 40

So the old person is 40yrs older than young one.

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