Here is another for fun question. must show all workings
so,
what is the biggest 4 digit whole number that meets the three requirements
1. the digits are different
2. the largest digit is equal to all of the other 3 digits added together
3. if you multiply the digits with each other, the result is evenly divisble by 10 with no remainders and is not equal to zero
also do not copy

For the product of the digits to be divisible by 10, it must have 10 as a factor, of course. Since 10 can't act as a digit, this means two of our digits must be 2 & 5.

No digit can be 0 because this would give a total product of 0.

Neither 2 nor 5 can be our largest because the lowest you can get is 1+2+3=6.
The lowest possible largest digit would have to be 1+2+5=8.
As for 9, this is not an option, and here's why: We need that 2 and 5, but to get 9 our other digit would have to be 2, which is a repeat.

So, our digits are 1, 2, 5, and 8.
It doesn't matter which order they are in. (take a look at the rules)
Therefore, we should put the highest digits in the highest value places.

The answer is