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# averages in C# programming

Posted on 2007-08-11
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Hi Im trying to understand c# programming.

Im trying to find a code in C# programming that will find the average of all the prime numbers between 1 and 100 and prints this average on screen.  I have been trying myself but im getting nowhere.
can anyone help me with this.  im trying to figure this out by sunday thanks
0
Question by:soundwire
• 4
• 3

LVL 143

Expert Comment

ID: 19676968
what do you have already?
* calculating the prime numbers?
* totalling those numbers?
* counting those numbers?
* dividing the total by the number?
0

Author Comment

ID: 19676979
I put in a code and it displayed all the numbers 1 through 100 but that it.  I dont know if that is th right track or not
0

LVL 143

Expert Comment

ID: 19676983
so, I guess you don't have yet a function to check if a number is a prime number...
have you searched already around in the internet for just that functionality?
0

Author Comment

ID: 19676992
yes and came up with nothing.
0

LVL 143

Expert Comment

ID: 19677003
then, you don't search hard enough, I found several good hits on the first try...

0

Author Comment

ID: 19677011
I tried ask.com , yahoo and google there are the 3 main engines that i get accuate info from. unless i needed to be more specific
0

LVL 37

Accepted Solution

gregoryyoung earned 1500 total points
ID: 19677013
quick google gave this ...

/// <summary>
/// This method should return whether or not an integer is a prime number
///
/// Please note that the solution should be as efficient as possible and not be breakable.
/// </summary>
/// <param name="number">Integer to be tested</param>
/// <returns>true or false</returns>
public static bool IsPrime(int number)
{
// Throw out impossibles
if (number < 2)
{
return false;
}

// Don't need to test above the square root of a number
for (int i = 2; i < (number); i++)
{
// If remainder is 0, number is not prime
if (number % i == 0)
{
// return false
return false;
}
}

// If all conditions are met, return true
return true;
}

from there its just a matter of keeping two variables (total and count) then divide.

pseudocode

for(int i=0;i<100;i++) {
if(IsPrime(i)) {
total += i;
count ++;
}
}
Console.WriteLine("there were " + count + " primer numbers. Average value is " + total/count);

Cheers,

Greg
0

Author Comment

ID: 19677310
thanks ill try that
0

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