Maximum value of D
Let X be any 3 digit number.
Let Y be the number obtained by reversing the digits of X.
Let D = X - Y.
What is the maximum value of D ?
PS : Please assume that the first digit of any of the three digit numbers cannot be zero.
The answer is 792.
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1 solution
Let X be written as
100 a +10 b+c where 0 <=a,b,c<= 9.
Y is equal to 100 c + 10 b + a.
D = X - Y or 99*(a-c).
Max occurs when a - c is equal to 8.
Hence D = 792.
Sample values of X,Y,D
901,109,792
981,189,792
971,179, 792.