Question 844111: Without using a calculator, test each of the following
numbers for divisibility by 2, 3, 4, 5, 6, 8, 9, 10, and 11:
a. 4,201,012
b. 1001
c. 10,001
Answer by Fombitz(32388)   (Show Source):
You can put this solution on YOUR website! 2 - last digit divisible by 2.
3 - Add the digits, the sum must be divisible by 3.
4 - last 2 digits divisible by 4
5 - ends in 5 or 0
6 - divisible by 2 and 3
8 - last 3 digits divisible by 8?
9 - Add the digits, the sum must be divisible by 9.
10 - last digit is 0.
11 - Add the odd positions starting from left to right. Add the even positions starting from left to right. If the difference of the sums is zero or a multiple of 11, the number is divisible by 11.
a) 2, yes
3, no, sum is 10
4, yes, 12/4=3
5, no
6, no
8, no
9, no
10, no
11, no, difference in sums is (4+0+0+2)-(2+1+1)=6-4=2
Now do the same for b and c.
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