A reading list contains 3 historical books and 4 science-fiction books. What is the probability that Tena will randomly choose a historical book for her first repost and a science-fiction book for her second?

a. 12/49

b. 2/9

c. 2/7

d. 1 2/7

There are 7 books all in all. Since the order is important, there are 7P2 (permutation of 7 taken 2) ways in which Tena can do the repost. If she picks historical books first then followed by the science-fiction, there are

3 x 4 = 12 ways.

The probability is therefore equal to 12 / (7P2) which is equal to 2/7. The answer is letter c.