Let A be the set of all strings of decimal digits of length 5. For example 00312 and 19483 are two strings in
A.
You pick a string from A at random. What is the probability that
(a) the string begins with 7575.
(b) the string has no 4 in it.
In questions 13-16 you have 40 diﬀerent books (20 math books, 15 history books, and 5 geography books).

Question

Quizplus · Accepted Answer

The Answer is (a)

10 / 10 ^ { 5 }

.
(b)

9 ^ { 5 } / 10 ^ { 5 }

Let a Be the Set of All Strings of Decimal