Computer assisted Instruction undeclared identifier error

I wrote code for a computer asssisted instruction program for multiplication but every time I build and debug I get undeclared identifier errors. I cannot figure out why they are errors. Here is my code and the errors I receive. Please help.


#include<iostream>
#include<cstdlib>
using namespace std;

//function prototypes
void problemGeneration(int, int, int);
void checkAnswer(int&, int, bool);
//declare global variables to be passed into functions

int main()
{
int num1 = rand() % 10;//random number between 0 and 9
int num2 = rand() % 10;//random number between 0 and 9
int answer = 0;
int product = num1 * num2;
bool isCorrect = false;
problemGeneration(num1, num2, answer);
checkAnswer(answer, product, isCorrect);
}

void problemGeneration(int num1, int num2, int answer)
{
cout <<"How much is" << " "<< num1 <<" " <<"times" << num2 << "?" << endl;
cin >> answer;
}

void checkAnswer(int &answer, int product, bool isCorrect)
{

if(answer == product)
{
isCorrect = true;
if(isCorrect = true)
{
cout << "Very Good!"<< endl;
problemGeneration(num1, num2, answer);
}
}
else
{
isCorrect = false;
cout << "No. Please Try Again. " << endl;
cin>> answer;
}
}



1>c:\users\jason\documents\visual studio 2008\projects\computer-aided instruction\computer-aided instruction\computer-aided instruction.cpp(36) : error C2065: 'num1' : undeclared identifier
1>c:\users\jason\documents\visual studio 2008\projects\computer-aided instruction\computer-aided instruction\computer-aided instruction.cpp(36) : error C2065: 'num2' : undeclared identifier

1st, use code tags.
Secondly, num1 and num2 aren't available in ProblemGeneration, hence the error.
Thirdly, good article for reading: SourceForge.net: Do - cpwiki not remove parameter names
And finally, update to Visual Studio 2010 if you can.

first, wrap your code in code tags and indent it properly.

second, you're declaring num1 and num2 in main() and then trying to use them in checkAnswer(). you cannot do this unless you make them global or pass them in as parameters.