Re: BDMO Regional Junior P8
Posted: Sat Apr 03, 2021 2:00 pm
Why can't we create combinations of 4 numbers on all those subsets? Would you please explainMehrab4226 wrote: ↑Fri Apr 02, 2021 9:32 pmwe cannot create combinations of 4 numbers on all those 5 subsets. And the answer should be 48.M F Ruhan wrote: ↑Fri Apr 02, 2021 2:12 pmSolution 1:
At first consider 1 such simple subset {1,2,3,4,5}
Now we can create any combination this subset by using numbers 6,7,8,9
for example: {1,2,3,4,5,8,9}
Total number of combination for this subset should be 4C4+4C3+4C2+4C1=15
As we can create total 5 simple subsets. So the total number of subsets should be 5*15+5=80