Question
Question: Number of combinations of 3 letters from 3A's 4B's and 5C's is:...
Number of combinations of 3 letters from 3A's 4B's and 5C's is:
A
10
B
12
C
9
D
None of these
Answer
10
Explanation
Solution
Total letters = 12 (3A's, 4B's, 5C's)
Case I: All three letters alike 3C1=3
Case II: 2 letters alike, 1 letter different3C1x2C1=6.
Case III: All three letters different = 1
Total = 10.