How many different 5 digit numbers can be formed
from the digit 1,2,3,4 and 5 if
(i). They are no restrictions on the digit and repetitions are allowed.Choose the 1st digit 5 ways.
Choose the 2nd digit 5 ways.
Choose the 3rd digit 5 ways.
Choose the 4th digit 5 ways.
Choose the 5th digit 5 ways.
5×5×5×5×5 = 55 = 3125 ways
(ii). The number is odd and no repetitions are allowed.Choose the 5th digit 3 ways. (either 1,3, or 5)
Choose the 1st digit 4 ways.
Choose the 2nd digit 3 ways.
Choose the 3rd digit 2 ways.
Choose the 4th digit 1 way.
3×4×3×2×1 = 72 ways
(iii).The number is even and reputations are allowed.Choose the 5th digit 2 ways. (either 2 or 4)
Choose the 1st digit 5 ways.
Choose the 2nd digit 5 ways.
Choose the 3rd digit 5 ways.
Choose the 4th digit 5 ways.
2×5×5×5×5 = 2×54 = 1250 ways
(iv). The number is greater than 50 000 and no repetitions are allowedChoose the 1st digit 1 way. (as 5)
Choose the 2nd digit 4 ways.
Choose the 3rd digit 3 ways.
Choose the 4th digit 2 ways.
Choose the 5th digit 1 way.
1×4×3×2×1 = 60 ways
Edwin