The number lock of  a suitcase has 4 wheels, each labelled with ten digits i.e. from 0 to 9. The lock opens with a sequence of four digits with no repeats. What is the probability of a person getting the right sequence to open the suitcase.

Explanation

Number of wheels in number lock of suitcase =4.

Now, first wheel can have any one of the tens digits from 0 to 9.

Since, repetition is not allowed, so second wheel can have any of the remaining 8 digits.

Similarly, third wheel can have any of the remaining 7 digits
.
And fourth wheel can have any of the remaining 6 digits

So, number of four digit lock code that can be formed without repetition of digits
=10×9×8×7=5040

So, total four digit numbers formed =5040

But since, the lock can open with only one of the all four digit numbers.

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