Twice the sum of its digits
Number Theory
Level
2
What is the only positive integer that is twice the sum of its digits?
The answer is 18.
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1 solution
The required number should be double digit digit, therefore let say the number is 10a + b , where a and b are positive integers from 0 to 9
Now, applying the given condition i.e.
10a + b = 2(a + b)
8a = b
This implies that a = 1 & b = 8 The required number is 18