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Odd number beetween 11 and 21 product of two prime numbers

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Kolbrun Gunnarsdottir

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Posted on Feb 06, 2015


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Hii,here is list of basic real numbers properties applying them you can solve the problems easily.

Assuming a,b,c,d are real numbers:

1)Commutative Property
a) Property of Addition: a+b = b+a
b)Property of Multiplication: ab = ba

2)Associative Property
a)Property of Addition: (a+b) + c = a + (b + c)
b)Property of Multiplication: ( ab )c = a ( bc )

3)Additive Identity:
a+0 = a where 0 is the additive identity
4)Additive Inverse:
For real number a, there exists -a such that
a+(-a) = 0
5)Multiplicative Identity:
For real number a,
1 X a = a
where 1 is the multiplicative identity
6)Multiplicative Inverse:
For real number X where a≠0, there exists 1/asuch that
a X(1/a) = 1
7)Zero Product Law:
If ab = 0, then a=0 or b=0 or both a and b = 0.

8)Distributive Properties:
a)Left distributive law
a (b + c ) = ab + ac
b)Right distributive law
(a + b) c = ac+ bc

Posted on Jun 14, 2010


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How many types of whole numbers do we have

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Eight of the first twenty numbers are prime, so the probability is 8/20 or 0.4 .

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I cant understand prime numbers

A prime number is a positive whole number (natural number) which cannot be divided into smaller whole numbers. In short, it can only be divided (integer division) by itself and 1.
First prime number is 2, then 3, 5, 7, 11, 13, 17, 19,
To generate a list of prime numbers the Greek Eratoshenes used a method called now the sieve Eratosthenes.

  1. Write all the natural numbers up to some chosen limit (100, 259, any limit )
  2. Remove 1 by crossing it ( 1 is no longer considered prime).
  3. The first prime number is 2. Circle the number 2.
  4. Go through the whole list crossing out all the numbers that are multiple of 2, that is 4, 6, 8,10,12, ...
  5. Repeat.
  6. The next prime number is 3 since it was not crossed out as a multiple of 2. Circle 3.
  7. Go through the whole list crossing all the numbers that are multiples of 3, and which have not already been crossed out as multiples of 2 .
  8. Number 4 has been crossed out already.
  9. Next prime number is 5. Circle 5
  10. Go through the whole list crossing all the numbers that are multiple of 5 and which have not been crossed out already as multiples of 2, or 3
  11. Repeat:
  12. Next prime number is 7. Circle 7
  13. Go through the whole list again, crossing out the multiples of 7, and so on.
If you want to test the primality of a positive integer (odd number) starting by dividing it by 3 (use divisibility rules or otherwise), then divide by 5, by seven, and all subsequent prime numbers. If it is not divisible by any prime number, keep going but do not exceed the prime number that is closest yet smaller than square root of your number.


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What is a prime number

a prime number is a number that can only be multiplied by itself and 1 - example 3 can only be multiplied by itself and 1.

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Is 1 a prime number

No, 1 is not a prime number. The decomposition of a number into prime factors must be unique so 2=1x2 is prime but since 1 can be written as 1=1x1x1x1....x1 with an arbitrary number of factors this opens up a can of worms as far as unicity of the decomposition is concerned. Conclusion: 1 has been ruled out as a prime number.
I hope that this gives you an idea why 1 is no longer considered prime.

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How to explain that all numbers ending with 1,3,5,7,9 are prime other words can I say that all odd numbers are prime numbers?

No not all odd numbers are prime numbers. A prime number is one that cannot be divided equally by any other number then itself or 1. Therefore numbers such as 9 is not a prime number because it can also be evenly divided by 3Hope this answers your question. Thank you.

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1 Answer

What is p(even or prime) for a single die roll

Even numbers = 2 , 4 , 6

Prime numbers = 3, 5

there fore total probability of getting either even or prime number in single die roll = 5/6

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What is the probability of rolling a even number or a prime number on a number cube? write fraction in simplest form

even nos: 2,4,6

prime nos:2,3,5

ie 1 is the only no. which is not desired

probability of getting one=1/6

hence probability of getting either even or prime no is
= 1-1/6 = 5/6

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1 Answer

Which number under 100 has the most primed factors

Hi johnhboland
Prime numbers are 2,3,5,7,11,13,17,23 .........
Take different combinations from the above list and multiply making sure you don't exceed 100

2x3x5 =30
2x3x7 =42
2x3=11 =66
2x3x13 =78
2x5x7 =70
I would say the answers are 30, 42, 66, 78, and 100 all have 3 prime factors
If repetition of the same factor is allowed:
answers would be 64 and 96 both having 6 prime factors
Have a good day

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