In how many different ways can the letters of the word BANANA be arranged?
Aptitude
Permutation and Combination
Difficulty: Easy
Choose an option
-
A60
-
B120
-
C360
-
D720
-
ENone of these
Answer
Correct Answer: 60
Explanation
### Concept & Formula
When a word has $n$ total letters but contains sets of identical letters, the number of distinct permutations is found by dividing the total factorial by the factorial of each repeating letter's frequency.
$$P = \frac{n!}{p! \times q!}$$
### Step-by-Step Solution
- **Given:** The word 'BANANA'.
- Count the total number of letters: $n = 6$.
- Identify repeating letters: The letter 'A' appears $3$ times, and the letter 'N' appears $2$ times.
- Set up the equation: Total valid arrangements = $\frac{6!}{3! \times 2!}$.
- Expand and simplify: $\frac{6 \times 5 \times 4 \times 3!}{3! \times 2 \times 1}$.
- Cancel out the $3!$ from numerator and denominator: $\frac{6 \times 5 \times 4}{2} = \frac{120}{2} = 60$.
### Exam Strategy & Shortcut
Always cancel out the largest factorial in the denominator with the expanded numerator first. Doing $\frac{6 \times 5 \times 4}{2}$ mentally takes only a few seconds compared to computing $720 / 12$.
### Common Pitfall
Only dividing by the factorial of one repeated letter (e.g., dividing only by $3!$ for the 'A's) and forgetting the 'N's entirely, which leads to the trap answer of $120$.
### Final Answer
Therefore, the correct answer is **60**.