Notes

using System;
using System.Diagnostics;
class Calculator
{
public static void Main()
{
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();

//Required requwsts from the user

Console.Write("max time (min)=" );
double t = double.Parse(Console.ReadLine());
double time = t;
time = stopwatch.ElapsedMilliseconds / 1000.0;

Console.Write("Max Question=");
int q = int.Parse(Console.ReadLine());

//New Random object
Random rand = new Random();

int w = 1 ;

while ((stopwatch.ElapsedMilliseconds<=time) &&( w< q))
{
int nb1 = rand.Next(1, 200); // nb1 in [1..200]
int nb2 = rand.Next(1, 50); //nb2 in[1...50]

//write the question & read the answer
Console.Write(nb1 + "/" + nb2 + "=" );
int e = int.Parse(Console.ReadLine());

//check if the answer is corret
if (e == (nb1 / nb2))
{
Console.WriteLine(nb1 + "/" + nb2 + "=" + (nb1 / nb2) + "Good");

}
else
{
Console.WriteLine(nb1 + "/" + nb2 + "=" + (nb1 / nb2) );

}

w++;

}

Console.WriteLine("------------------------------");
if (q >= time)
{
Console.WriteLine("Question count= " + q);
}

//Time spent
System.Console.WriteLine( "Time = " + stopwatch.ElapsedMilliseconds/60000+ " min .");




}
}