How many 3-digit numbers can be formed from the digits 1,2,3,4 and 5 when repetition of digits is allowed and if repetition of digits is not allowed.......
There are five digits, 1,2,3,4 and 5. Every digit can be selected any number of times. Hence , we can select first digit five times. The second digit 5 times and the third digit five times.
Therefore the number of ways in which the selection of three digits can be made 5x5x5x ways = 125 ways.
Under the condition , first digit can be selected 5 ways. After the selection of first digit four digits are left. Second digit can be selected in four ways and third digit can be selected in three ways.
Therefore The total number of ways of selecting three digits is 5x4x3 = 60 ways.......
Sol :
When Repetition is allowed :
Therefore the number of ways in which the selection of three digits can be made 5x5x5x ways = 125 ways.
When repetition is not allowed :
Under the condition , first digit can be selected 5 ways. After the selection of first digit four digits are left. Second digit can be selected in four ways and third digit can be selected in three ways.
Therefore The total number of ways of selecting three digits is 5x4x3 = 60 ways.......
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