Question

Greg forms two numbers with the digit 1,2,3,4,5 and 6 both numbers have three digits ang each digits is used only once greg adds these two numbers what is the greatest sum greg can obtain

Answer 1

Largest sum is possible if 6 & 5 appear in the hundredth places in the two numbers.

We are left with 1,2,3,4.

Largest sum is possible if 3 & 4 appear in the tens places.  Finally 1 & 2 appear in the units places.

So the numbers are  either  641 & 532 ,  or   631 & 542  ,  or   642 & 531  or  632 & 541.

Then the greatest sum = 1,173

There are 4 combinations of the two numbers possible.