Answers

2014-03-17T18:55:26+05:30
Start from smallest digit and then go to biggfer or try to add those no which can form mutiple of 10 that's all
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2014-03-17T18:57:14+05:30
First you can add all tens,hundreds and thousands then you can add the remaining places.

sum is easiest one when compare to product and difference.
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