Permutation and combination Help please, medal and fan!

We are arranging 4 digits from the set {0, 1, 2,..., 9} and not allowing repetition. The two
restrictions we must honor are that the digit 0 cannot appear in the thousands' position and that
the units’ digit be odd. Number of ways to achieve this is
A) 9000
B) 4500
C) 7759
D) 2240

Explain me the whole process please

Question

Permutation and combination Help please, medal and fan! 

 We are arranging 4 digits from the set {0, 1, 2,..., 9} and not allowing repetition. The two
restrictions we must honor are that the digit 0 cannot appear in the thousands' position and that
the units’ digit be odd. Number of ways to achieve this is
A) 9000
B) 4500
C) 7759
D) 2240 

Explain me the whole process please

gentorr · Answer

what did i just read O_. lol

deadpooi · Answer

4th place (ones) can be filled in 5 ways (1,3,5,7,9) 

1st place (thousandth) can be filled in 8 ways (excluding 0 and the odd number already in 4th place) 


2nd place (hundreds) can be filled in 8 ways (excepting 1 odd number and the 1st digit) 

3rd place (hundreds) can be filled in 7 ways (excepting 1 odd number and the 1st two digits) 

therefore total no of ways = 5x8x8x7 = 2240 

Answer is D.

Click Best Response if helped kido.

anonymous · Answer

@DeadPooI  Thanks a lot! Even if you hadn't replied I'd be a fan cause duh, Deadpool.