PLUTO wrote:
Why not answer 190? there will be 20 combinations where m=n example {12,12}, {13,13}. We need to take out those 20 combinations from 210.
Hey
PLUTOWelcome to GMATClub!
We only choose different integers, as the number of ways of choosing the integers is \(\frac{21*20}{2} = 210\).
If what you said was possible, the number of ways of choosing the integers are 21*21 = 441
and we will eliminate 21 options - (12,12),(13,13).......(31,31),(32,32). This will bring down
the number of options to 441 - 21 = 420. Now, since (12,21) is the same as selecting (21,12)
we will have to eliminate those options(which are exactly half of the options). Therefore, the
total number of ways of choosing the integers are \(\frac{420}{2} = 210\)
Hope this clears your confusion.
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