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g100num [7]
3 years ago
8

What percent? What percent of the first 20 natural numbers are prime numbers?

Mathematics
2 answers:
Mice21 [21]3 years ago
7 0
Let's find all the prime numbers.

1,3,5,7,9,11,13,15,17,19

They are not divisible by 2.

Put that into a fraction, where the amount of numbers is the numerator and the total amount of numbers is the denominator.

10/20

That is half of 20.

So, 50% of the 20 first natural numbers are prime.

I hope this helps!
~cupcake
Ede4ka [16]3 years ago
6 0
Prime numbers: 2, 3 , 5, 7, 11, 13, 17, 19= 8/20 numbers.
8/20= 4/10 4/10=2/5
2/5= 40%
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How do you do number 1?<br>Whenever I tried to answer it, I always get fraction. help me.​
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Answer:

The pairs are (13,15) and (-15,-13).

Step-by-step explanation:

If n is an odd integer, the very next odd integer will be n+2.

n+1 is even (so we aren't using this number)

The sum of the squares of (n) and (n+2) is 394.

This means

(n)^2+(n+2)^2=394

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n^2+n^2+4n+4=394               since (a+b)(a+b)=a^2+2ab+b^2

Combine like terms:

2n^2+4n+4=394

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Divide both sides by 2:

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15 and -13 since 15(-13)=-195 and 15+(-13)=2

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n+15=0

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Add 13 on both sides:

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Let's check both results

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(-15)^2+(-13)^2=225+169=394.  So (-15,-13) looks good!

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