How many 3-digit numbers can be formed from the digits 1, 2, 3, 4 and 5 assuming that (i)         repetition of the digits is allowed? (ii)        repetition of the digits is not allowed?

Explanation

(i)A three digit number is to be formed from given 5 digits `1,2,3,4,5.`

Now, there are 5 ways to fill ones place.

Since, repetition is allowed , so tens place can also be filled by` 5` ways.

Similarly,hundreds place can also be filled by 5 ways.

So, number of ways in which three digit numbers can be formed from the given digits is `5×5×5=125`


(ii)Since, repetition is not allowed , so tens place can be filled by remaining `4` digits.

So, tens place can be filled in 4 ways.

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