Question

The sum of two digit number is 81 less than number. what is the difference between the digits of the number

Answer 1

Acctually you cannot Determine The difference of two digits. Why? let's see

90
sum 9+0= 9
which is 81 less than 90
90-81 = 9

91
sum = 9+1 = 10
which is 81 less than 91
91-81= 10

99
sum 9+9 = 18
which is 81 less than 99
99-81 = 18

which holds true for 90 to 99

Now see mathematically

let first digit be X and 2nd be Y

Number = 10X + Y
(in junior classes you must have written no. in expanded form)

According to question

X+Y = (10X+Y) - 81

X+Y-Y = 10X - 81
-9X = -81
X = 9

Acctually you cannot figure out what Exactly Y is........

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