This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Since we have A B C D ≡ 1 1 ( m o d 1 5 ) , we know that 15 divides A B C D − 1 1 evenly.
From A ≡ 1 ( m o d 7 ) we know that A = 1 / 8 .
From A B ≡ 0 ( m o d 7 ) we know that i f A = 1 , t h e n B = 4 ; i f A = 8 , t h e n B = 4 . We conclude that B = 4
From C ≡ D ≡ 1 ( m o d 5 ) we know that C = 1 / 6 , D = 1 / 6
From C + A ≡ 0 ( m o d 7 ) we can work out C . All possible values of C + A are: 1 + 1 = 2 ; 1 + 8 = 9 ; 6 + 1 = 7 ; 6 + 8 = 1 4 . We conclude that C = 6 .
Now we know that our number looks like this: A 4 6 D . There are four numbers that can be made up with currently possible values of A and D , however, only one of them is evenly divisible by 1 5 when it is subtracted by 15.
Possible numbers are: 1 4 6 1 ; 1 4 6 6 ; 8 4 6 1 ; 8 4 6 6 .
Answer: 1 4 6 6