Math Is Fun Forum

chetah

Member

Registered: 2008-02-15

Posts: 32

Discrete Math Pseudocode

Following the execution of this program segment, which value of n is printed?
N = 3
Sum = 0
While sum < 10,000 do
    Begin
        N = N + 7
        Sum = sum + n
    End
Print N

I am able to check my answer by typing in the code above.  My question is, how do I approach this question in an examination setting?  It would take forever to trace.

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Discrete Math Pseudocode

come up with a recurrence relation for n and sum, then find the close form solution.

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

chetah

Member

Registered: 2008-02-15

Posts: 32

Re: Discrete Math Pseudocode

Explain the concept of close form for me please.

Dragonshade

Member

Registered: 2008-01-16

Posts: 147

Re: Discrete Math Pseudocode

correct me if I am wrong

Last edited by Dragonshade (2008-04-05 21:45:34)

chetah

Member

Registered: 2008-02-15

Posts: 32

Re: Discrete Math Pseudocode

Not quite certain, when I typed it on my system, the result is something like 1118.

Dragonshade

Member

Registered: 2008-01-16

Posts: 147

Re: Discrete Math Pseudocode

But I test it with C++ , I got 374 as well

#include <iostream>

using namespace std;

int main()
{
  int n=3;
  int Sum=0;
do
{
    n=n+7;
    Sum = Sum+n;
}while (Sum < 10000);

cout << n;

return 0;
}

chetah

Member

Registered: 2008-02-15

Posts: 32

Re: Discrete Math Pseudocode

you are correct, I was testing a number greater than 3.