Question 1082595: SetA={1,2,3,4,5,6,7,8,9} .if B={a,b,c}be the subset of A where a+b+c is multiple of 3. Find no. Of such subsets?
Answer by richard1234(7193)   (Show Source):
You can put this solution on YOUR website! The only possible cases for B are where all elements are the same (mod 3), or all elements are different (mod 3).
If all elements are the same (mod 3), we have 3 subsets: {1,4,7}, {2,5,8}, {3,6,9}.
If all elements are different (mod 3), then we have 3 ways to choose an element from 1,4,7; 3 ways to choose an element from 2,5,8; 3 ways to choose an element from 3,6,9, giving 3*3*3 = 27 ways.
Total number of subsets = 3+27 = 30
|
|
|
