Question

How many five digit numbers can be formed from the set of nine numbers (0,1,2,3,4,5,6,7,8) if no number is repeated and no number starts with zero and
a) there are no other restrictins
b) the result must be an odd number

Answer 1

a) no restrictions, except can't start with a zero
so 8x8x7x6x5 = 13440

b) has to be odd, not start with zero
has to end with odd number, there are 4 of these
can't start with zero, leaving 7 (remember one is already gone in the odd spot)

number of cases = 7x7x6x5x4 = 5880

Answer 2

thank you!