How many different four-letter passwords can be formed from the letters upper a comma upper b comma upper c comma upper d comma upper e comma upper f comma and upper g if no repetition of letters is allowed?

Answer with explanation:

Number of Letters from which we have to make four-letter passwords

   ={A,B,C,D,E,F,G}=7

Since repetition of digit is not allowed.In Permutation order of arrangement is Important,while in combination order of arrangement is not Important.

Out of seven letters we have to select four letters, keeping in mind the order of Alphabets.So, we will use the concept of Permutation.

Number of ways of arrangement,that is to make four letter password from 7 Alphabets

So, total number of ways of making password from 7 alphabets=840 ways

Second Method⇒

Since repetition of alphabets is not allowed, first Alphabet can be chosen in 7 ways , second alphabet can be chosen in 6 ways, third alphabet can be chosen in 5 ways, fourth alphabet can be chosen from four alphabets.

So, total number of ways of making four letter password

       =7×6×5×4

    = 840 ways

i can't see the picture : /

question 1 is 8, question 2 is 9, question 3 is 24

step-by-step explanation:

now, the numbers they give you at the top are the key. from there, you just have to plug and chug! let's try 1, 2, and 3!

key: a=3, b=5, c=6

1. a+5

remember, a=3, so we plug that in to get 3+5=8

2. 15-c

c=6, so we plug that in to get 15-6=9

3. 4b

b=6, so we plug it in to get 4*6=24

time to try the rest on your own! if you put the answers below in a comment, i'll check them for you!