How many 3-digit numbers can be formed from the digits 1, 2, 3, 4 and 5 assuming (i) repetition of digits allowed. (ii) repetition of digits now allowed?

units place can be filled in 5 ways

similarly, tens place can be filled in 5 ways

hundreds place can be filled in 5 ways

Therefore, no. of 3 digit numbers when repetition allowed = 5 x 5 x 5 = 125

(ii) Since repetition is not allowed,

units place can be filled in 5 ways

tens place can be filled in 4 ways

hundreds place can be filled in 3 ways

Therefore, no. of 3 digit numbers when repetition is not allowed = 5 x 4 x 3 = 60