1 0 1 1 3 1 1 1 0 3 1 1 0 1 3
Which of the base 3 integers above is divisible by 3?
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We see that 1 0 1 0 is divisible by 10 and 1 0 2 is divisible by 2. Hence, we can say that a number who ends with 0 is divisible by the base in which it is written. So, 1 1 1 0 3 is the only number to be divisible by 3
We can say it but not because it works for 10 and 2, because the rightmost digit of a number in base n is the division of said number by n. Hence if 0 is the remainder, it is divisible.
1 0 1 1 3 = 3 3 + 3 1 + 3 0 3 3 3 + 3 1 + 3 0 = 3 2 + 1 + 3 1 1 1 1 0 3 = 3 3 + 3 2 + 3 1 3 3 3 + 3 2 + 3 1 = 3 2 + 3 1 + 1 1 1 0 1 3 = 3 3 + 3 2 + 3 0 3 3 3 + 3 2 + 3 0 = 3 2 + 3 + 3 1
Therefore, it is obvious that 1 1 1 0 3 is divisible by 3
Generally, for any positive number x in base n
x is divisible by n if the last digit is 0
(a+b)%base=(a%base+b%base)%base
By this, we know that except the units place all the other positions always yield a multiple of base...in case if a rightmost bit is set, then 1 will be added, which when base>1 will always yield a remainder of 1...To say that the number is divisible by some number, we need to make the remainder 0...Title is the hint to get solution...(1110) is the solution here...
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Relevant wiki: Integer Number Bases
1 1 1 0 3 = ( 3 3 × 1 ) + ( 3 2 × 1 ) + ( 3 1 × 1 ) + ( 3 0 × 0 ) = 3 9 which is divisible by 3.
We can see that the other options are not divisible by 3.