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.
24
25=20,21,23
6 They are 799, 979, 997, 889, 898 & 988
The number 9 is the maximum number of beads on an abacus because it is the last number in the ones place before the tens place is reached.. The abacus is a tool that was used for arithmetic in ancient times. It is composed of a frame with a series of rods or wires on which beads are strung. The beads are used to represent numbers.
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.
9999
100,000
There are 504 such numbers.
There are 5! = 120 such numbers.
512
12
840
823543