Question

Mimi has six books from the Statistics is Fun series. She plans on bringing two of the six books with her in a road trip.

(a)How many different ways can the two books be selected?

(b)Please describe the method used and the reason why it is appropriate for answering the question.

Answer 1

a) Number of ways to select 2 books from 6 = 6C2

= 6!/(2! x (6-2)!)

= 6!/(2! x 4!)

= 6x5x4!/(2! x 4!)

= 6x5/2

= 15

b) She draws to books from a set of 6, without replacement and the order of selection of books is not important. Thus, we are calculating the number of possible combinations of 2 items from a set of 6 items. This can be calculated using Combination formula.

Combination formula: Number of ways to select r item from n give items = n!/(r! x (n-r)!)