Since there are no restrictions on the strings, we can think of this problem as drawing 5 random digits in sequence. There is a 9/10 chance each time we draw to NOT get a 4. Every time we draw, we multiply by 9/10 again until we've draw 5 digits. Thus, the answer is (9/10)^5 :)

Step-by-step explanation:

See Comment for Complete Question

Given that A has 5 digits. A digit in A can be chosen from 0 to 9 (10 digits).

However, selection without 4 means that we can only select from 0 to 3 and 5 to 9 (altogether, that is 9 digits)

The probability of selecting a number other than 4 in each of the digit is:

So, the required probability is:

what is all that apply?

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: