Hello

umg,

I too had the same concern. I did some digging on this and found some interesting properties. You too may find them useful.

Sum of individual sums of a number is called Digit sum or Beejank (in Vedic maths). One shortcut to quickly arrive at the digit sum is to simply ignore 9's. Let me take the first option - 94123. The Digit sum is -

~~9~~ +

~~4~~ + 1 +

~~2~~ +

~~3~~ = 1 (Simply strike out the digit 9 or the numbers that add up to 9. You can try it on others options and find that this holds true.

While I was at it, I also discovered that digit-sum/Beejank can be used to quickly check if the addition/multiplications done are correct. There are a lot of links that explain this approach. One such link is -

http://www.quickermaths.com/checking-of ... out-nines/umg wrote:

I think this is a poor-quality question and I agree with explanation. Because there is no shorter way to solve this question.

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