Question 1044205: Jess has a 4-digit code for her lock, but she has forgotten two of the digits.
? 8 5 ?
Jess knows that her 4-digit code is:
. less than 4000
. odd
. divisible by 3
. made up of 4 different digits
How many 4-digit codes are possible?
(A) 3 (B) 5
(C) 6 (D) 10
Can someone show me the easy way for this number problem please.
Thank you!
Found 2 solutions by ankor@dixie-net.com, kelvin nyawali:
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Jess has a 4-digit code for her lock, but she has forgotten two of the digits.
? 8 5 ?
Jess knows that her 4-digit code is:
. less than 4000
. odd
. divisible by 3
. made up of 4 different digits
How many 4-digit codes are possible?
:
Let's just start with what we do know. We can fine tune our method as we go along.
:
less then 4000, therefore the first 3 digit possibilities are:
185 _
285 _
385 _
:
final number is odd and not a repeat
:
The final digit of 185_: 3,7,9. With a calc see which ones are divisible by 3
1857 is so that's one possibility
:
The final digit of 285_: 1,3,7,9. With a calc see which ones are divisible by 3
2853 is therefore 2859 also has to be, (a difference of 6) so that's three possibilities
:
The final digit of 385_: 1,7,9. With a calc see which ones are divisible by 3
None are divisible
:
The answer is A. 3
Answer by kelvin nyawali(1)  (Show Source):
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