1.

The number of 5-digit number that can be made using the digits 1 and 2 and in which at laest one digits is different, isA. 30B. 31C. 32D. none of these

Answer» We have,
Required number of numbers
= Total numbres of 5-gigit numbers formed by the digits 1 and 2
- Number of 5-digit numbers formed by the digits 1 and 2 when numbers have all digits equal
`=2^(5)-2=30`.


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