How many numbers greater than 24,000 can be formed by using digits 1,2,3,4,5 when repitation is not allowed?
Answers
Condition 1 : Number must be greater than 24,000
Condition 2: No repeats
If the digit in the ten thousands place is 2:
Number of possible digit for ten thousands place = 1
(That is, the digit 2)
Number of possible digit for thousands place = 2
(They are the digit 4 or 5)
Number of possible digit for hundred place = 3
(They are any digits not used yet)
Number of possible digit for tens place = 2
(They are any digits not used yet)
Number of possible digit for ones place = 1
(They are any digits not used yet)
Possible combinations = 1 x 2 x 3 x 2 x 1 = 12
If the digit in the ten thousands place is 3, 4, or 5:
Number of possible digit for ten thousands place = 3
(That is, the digit 3, 4, or 5)
Number of possible digit for thousands place = 4
(They are any digits not used yet)
Number of possible digit for hundred place = 3
(They are any digits not used yet)
Number of possible digit for tens place = 2
(They are any digits not used yet)
Number of possible digit for ones place = 1
(They are any digits not used yet)
Possible combinations =3 x 4 x 3 x 2 x 1 = 72
Find total possible combination:
Total combination = 12 + 72 = 84
Answer: There are 84 possible combinations