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A letter lock consists of 4 rings each ring contains 9...

This question belongs to Arithmetic Ability Permutation And Combination
Permutation and Combination
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A letter lock consists of 4 rings, each ring contains 9 non-zero digits. This lock can be opened by setting four digit code with the proper combination of each of the 4 rings. Maximum how many codes can be formed to open the lock ?

Answer & Solution
Correct Answer: Option B
There are 9 non-zero digits to arrange themselves at 4 different position. Each letter can be arrange at different position in 9 different ways.
So, required number of ways,
= 9 × 9 × 9 × 9
= 94
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2 Comments
Kumar Chandan
Kumar Chandan 11 years ago
It is 9 to the power 4 not 94.
Nikhil
Nikhil 11 years ago
The multiplic of 9*9*9*9=6561 then how it come 94?
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