Question

how many 4 digit nos. greater than 3400 can be formed with the digits 0,1,3,5,7,9 if repitition of digits is not allowed

Answer 1

1st digit can not be 0,1
so for 1st digit there are 4 option
2nd digit can not be 0,1,3
so there are 3 option
so
so there will be 24 no.

Answer 2

1st digit can not be 0,1

so for 1st digit there are 4 option

2nd digit can not be 0,1,3

so there are 3 option

so

so there will be 24 no.