Re: Let x be a two-digit number. If the sum of the digits of x is 9, then
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14 Jan 2022, 03:50
Given,
This is the fastest approach you can use ( will come to your mind in a second or so after reading the question)
Sum of digits of x is 9. The two digit can be from {18, 27, ...., 90} = {2.9, 3.9, ... 10.9 }
Basically it is multiple of 9.
Now add 10 to each of these makes these {28, 37, . . . 100}
So all the sums will be 10 and for the 100 it will be 1.
The correct option is E. (10 or 1)