21
If the number is xy, it can be written as 10x+y 10x+y=7*(x+y) => 3x=6y =>x=2y The smallest xy is 21
Find a four digit number, with four different digits, that equal to the number formed by its digits in descending order minus the number formed by its digits in ascending order.
In any day before noon how many times is the sum of the digits of the time equal to 15? For instance 2:58 and 11:49 are two times when this is true.
