SOLUTION: what is the method of divisibility test by 7? by 11?

Question 1061669: what is the method of divisibility test by 7? by 11?
Answer by addingup(3677) (Show Source): You can put this solution on YOUR website!
7:
Double the last digit and subtract it from a number made by the other digits. The result must be divisible by 7.
Example:
672 (Double 2 is 4, 67-4=63, and 63�7=9) Yes, divisible by 7.
905 (Double 5 is 10, 90-10=80, and 80�7=11 3/7) Not divisible by 7.
:
11:
Add digit, subtract next digit, add next digit, and so on. Then the answer must be divisible by 11.
Examples:
1364 (+1−3+6−4 = 0) Yes
913 (+9−1+3 = 11) Yes
3729 (+3−7+2−9 = −11) Yes
987 (+9−8+7 = 8) No
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