Double the last digit and subtract the last digit from the remaining digits.
By tautology. If it did not work, it would not be a divisibility rule!
If a number is divisible by 5 and 7, it's divisible by 35.
What is the divisblity rule by 8
There is no easy rule for divisibility by 34.
The special divisibility rule of 17 is "Take the difference of the rest of the digits and the last digit times 5." For instance: 17 1 - 7 * 5 = 1 - 35 = -34 which is divisible by 17.
The number must be divisible by 2 and by 7.
By tautology. If it did not work, it would not be a divisibility rule!
2 x 7 x 7 = 98
If a number is divisible by 5 and 7, it's divisible by 35.
What is the divisblity rule by 8
There is no easy rule for divisibility by 34.
The special divisibility rule of 17 is "Take the difference of the rest of the digits and the last digit times 5." For instance: 17 1 - 7 * 5 = 1 - 35 = -34 which is divisible by 17.
The divisibility rule for 2 works because the base of our number system, 10, is divisible by 2.
Able to Be Divided
2.50
The divisibility rule for 42 isdivisibility by 2, ANDdivisibility by 3, ANDdivisibility by 7.Divisibility by 2 requires the number to be even. That means it must end in 0, 2, 4, 6 or 8.Divisibility by 3 requires that the digital root of the number is divisible by 3. That is, the sum of the digits is divisible by 3. If the first sum is large, you can calculate the digital root of the digital root (and again, if necessary) and check that for divisibility by 3.The divisibility rule for 7 is more difficult.Take the last digit (units).From the number formed by the remaining digit, subtract twice the last digit.If the answer is divisible by 7 (including zero or negative numbers), then the original number is divisible by 7.For large numbers, repeat the process to bring the number down to a manageable size.
Judging by some of the questions asked on this site, the first rule is that divisibility is a concept that applies only to whole numbers.