6
27 three digit numbers from the digits 3, 5, 7 including repetitions.
ten factorial = 10! = 3,628,800
from 100 to 999 it is 900
24 of them. So we have a 2 or 6 in the unit position, therefore (2)(4)(3) = 24 even three-digit numbers, can be formed.
There are 5*4*3 = 60 such numbers.
25=20,21,23
6 They are 799, 979, 997, 889, 898 & 988
9999
100,000
There are 7,290 different 4-digit numbers that can be formed from the digits 1-9 without repetition.
There are 504 such numbers.
512
12
There are 5! = 120 such numbers.
The number 1234567890 can create about 39 of 40 4 digit numbers.
There are 60480 numbers.
823543