Question

The permutations and combinations of abcd taken 3 at a time are respectively

Answer 1

1. Permutation of (a b c d) taken 3 at a time i.e order of alphabets is important is $_{3}^{4}\textrm{P}$=$\frac{4!}{(4-3)!}=\frac{4!}{1!}=4\times3\times2\times1=24$

2. Combination of (a b c d) taken 3 at a time order is not important i.e (ab c) and (c b a) are same=$_{3}^{4}\textrm{C}$=$\frac{4!}{(4-3)!\times3!}=\frac{4!}{3!}=\frac{4\times3!}{3!}=4$

Answer 2

Answer:

permutations= 24,  combinations = 4

Step-by-step explanation:

Number of letters in abcd = 4

Number of letters taken at a time = 3

Number of permutations= 4P3

Number of permutations = 4 x 3 x 2

Number of permutations= 24

Number of combinations = 4C3

Number of combinations = (4 x 3 x 2)/(1 x 2 x 3)

Number of combinations = 4

Answer: permutations= 24,  combinations = 4