the security gate at a storage facility requires a five-digit lock code. if the lock code must consist only of digits from 1-7 inclusive, with no repeated digits and the first and last digits must be odd, how many lock codes are possible?
so i am using the slot method to answer this.
1. _ _ _ _ _ < 5 digits.
2. (1,3,5,7) <4 digits are odd.
3. 4 _ _ _ 3
4. (0,2,4,6) <4 digits are even so now the numbers in the middle will have more choice. 2 numbers are still available from odd numbers so....
5. 4 6 5 4 3
6. 4x6x5x4x3=1440
but the mgmat book says the answer is 720. how?
so i am using the slot method to answer this.
1. _ _ _ _ _ < 5 digits.
2. (1,3,5,7) <4 digits are odd.
3. 4 _ _ _ 3
4. (0,2,4,6) <4 digits are even so now the numbers in the middle will have more choice. 2 numbers are still available from odd numbers so....
5. 4 6 5 4 3
6. 4x6x5x4x3=1440
but the mgmat book says the answer is 720. how?
