View written solutionFree
Correct answer: 309
We need the dictionary rank of the word MOTHER among all permutations of its letters.
The letters are:
Arrange them in alphabetical order:
Since all letters are distinct, we count how many valid permutations come before MOTHER in dictionary order.
Step 1: First letter = M
We count words beginning with a letter smaller than .
Smaller letters available:
For each such choice, the remaining letters can be arranged in:
So count:
Step 2: Fix first letter M, second letter = O
Remaining letters are:
Now count words beginning with and having second letter smaller than .
Smaller available letters than :
For each such choice, remaining letters can be arranged in:
So count:
Running total:
Step 3: Fix MO, third letter = T
Remaining letters are:
Now count words beginning with and having third letter smaller than .
Smaller available letters than :
For each such choice, remaining letters can be arranged in:
So count:
Running total:
Step 4: Fix MOT, fourth letter = H
Remaining letters are:
Letters smaller than : only
For this choice, remaining letters can be arranged in:
So count:
Running total:
Step 5: Fix MOTH, fifth letter = E
Remaining letters are:
Letters smaller than : none
So contribution:
Step 6: Fix MOTHE, sixth letter = R
Only one letter remains, so no additional permutations come before it.
Step 7: Add 1 for the word itself
So rank of MOTHER is:
Final Answer
The position of the word MOTHER is:
The derived answer matches the stored correct answer.
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