Question Detail

STA 112 PERMUTATIONS AND COMBINATIONS Objective Question

Question

What is the number of ways of arrangement of letters of the word 'BANANA' so that no two N's are together?
Options
A 40
Correct Answer
B 60
C 80
D 100
Correct Answer

Option A is the correct answer.

Detailed Explanation

The word BANANA has 6 letters: B, A, N, A, N, A. There are 3 A's and 2 N's.To ensure no two N's are together, first arrange the other letters: B, A, A, A.The number of ways to arrange B, A, A, A is 4! / 3! = 4.Now, place the 2 N's in the spaces created by these letters: _ B _ A _ A _ A _.There are 5 possible spaces. We need to choose 2 of these spaces for the two N's. This can be done in 5C2 ways = (5 * 4) / (2 * 1) = 10 ways.Therefore, the total number of arrangements where no two N's are together is 4 (arrangements of BAAA) * 10 (placing N's) = 40.

Hint

First arrange the letters other than 'N'. Then, place the 'N's in the gaps between the other letters.

Question Info