Question

How many different twotwo​-letter passwords can be formed from the letters

Answer 1

Answer:

$70$

Step-by-step explanation:

GIVEN: two two​-letter passwords can be formed from the letters  A, B, C, D, E, F, G and H.

TO FIND: How many different two two​-letter passwords can be formed if no repetition of letters is​ allowed.

SOLUTION:

Total number of different letters $=8$

for two two​-letter passwords $4$ different are required.

Number of ways of selecting $4$ different letters from $8$ letters$=^8C_4$

                                                                                                   $=\frac{8!}{4!4!}$

                                                                                                  $=70$

Hence there are $70$ different two-letter passwords can be formed using $8$ letters.