###### Asked in Math and ArithmeticPrime NumbersNumbers

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# Friendly number strategy for divisibility?

## Answer

###### Wiki User

###### November 11, 2008 10:43PM

I've never heard of a "friendly number strategy" per se; but there are specific rules for "divisibility" that you can use to help break up large numbers. For example, if the number is even, it is divisible by 2; if the sum of the numbers

## Related Questions

###### Asked in Math and Arithmetic

### What are the divisablity rules?

the divisibility rule for 2 is: The number is even;the last
digit ends with a 2,4,6,8,10, etc.
The divisibility rule fir 3 is: The sum of the number is divisible
by 3
The divisibility rule for 4 is: The last two digits are divisible
by 4
The divisibility rule for 5 is: The number ends with a 5 or 0
The divisibility rule for 6 is: The sum CAN be divisible by
2 and or 3
The divisibility rule for 9 is: The sum of the number is divisible
by 9
The divisibility rule for 10 is : The number ends with a 0

###### Asked in Math and Arithmetic

### What is the divisibility rule of 64?

There are two ways of answering this.
Check the number for divisibility by 2.
Check the quotient for divisibility by 2.
Check the quotient for divisibility by 2.
Check the quotient for divisibility by 2.
Check the quotient for divisibility by 2.
Check the quotient for divisibility by 2.
For large numbers, the check can be restricted to the number
formed by the last six digits.

###### Asked in Math and Arithmetic

### What are the 20 divisibility test?

To test divisibility for 20, you need to use the tests
for divisibility by 4 and 5.
The test for divisibility by 4 is that the last 2 digits
of the number, given as a 2-digit number, are divisible by 4.
Example for 4:
We are testing the number 11042.
42/4 = 10.5 which is not a whole number. Therefore 11042 is
not divisible by 4.
The test for divisibility by 5 is that the last digit of
the number is either 5 or 0.

###### Asked in Math and Arithmetic

### What are all the divisibility rules for 48?

Divisibility by 48 requires divisibility by 3 AND by 48
Divisibility by 3 requires tat the digital root (sum of digits)
is divisible by 3.
Divisibility by 16 requires that the number formed by the last
four digits is divisible by 16.
Of both these are satisfied by a number then it is divisible by
48.

###### Asked in Math and Arithmetic

### What is the divisibility rule for 42?

The divisibility rule for 42 is
divisibility by 2, AND
divisibility by 3, AND
divisibility 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.

###### Asked in Math and Arithmetic

### What is the divisibility rule for 22?

The divisibility rule for 22 is that the number is divisible by
2 and by 11.
Divisibility by 2 requires that the number ends in 0, 2, 4, 6 or
8.
Divisibility by 11 requires that the difference between the sum
of the the digits in odd positions and the sum of all the digits in
even positions is 0 or divisible by 11.