Implementing a timer into math game

[Joniniko]

Alright so basically i need to create a simple maths game in C. Involving addition subtraction and multiplication of random numbers. But i also need to add a timer to that. So lets say you are given 10 seconds to answer the question and every correct answer adds you 10 seconds. How would i implement this?
Here is what i got so far. Any other comments/suggestions about the code are welcome among with criticism as i want my code to be as efficient as possible and in good style.
Btw i'm required to use system("pause"); at the end, just to let you know that i did not do that on purpose.

#include <stdio.h>
#include <time.h>
#include <stdlib.h>  

int GetRand(int min, int max);

int main() {
	int x,y,z,i,cho,cor=0,err=0;

	printf("Please select what you would like to do\n1)Addition\n2)Subtraction\n3)Multiplication\n");
	scanf("%d",&cho);

	if (cho==1) {
     for(i=0;i<5;i++) {
	 x = GetRand(0, 100);
	 y = GetRand(0, 100);
	printf("%d + %d\n",x,y);
	scanf("%d",&z);
	if (z!=x+y) { printf("Wrong answer\n"); err=err+1; }
	if (z==x+y) { printf("Correct answer\n");  cor=cor+1;} }
	 printf("Correct answers: %d\nWrong answers: %d\n",cor,err);
	}

	if (cho==2) {
		for(i=0;i<5;i++) {
	 x = GetRand(0, 100);
	 y = GetRand(0, 100);
	printf("%d - %d\n",x,y);
	scanf("%d",&z);
	if (z!=x-y) { printf("Wrong answer\n"); err=err+1; }
	if (z==x-y) { printf("Correct answer\n");  cor=cor+1;} }
	 printf("Correct answers: %d\nWrong answers: %d\n",cor,err);
	}

	if (cho==3) {
		for(i=0;i<5;i++) {
	 x = GetRand(0, 15);
	 y = GetRand(0, 15);
	printf("%d * %d\n",x,y);
	scanf("%d",&z);
	if (z!=x*y) { printf("Wrong answer\n"); err=err+1; }
	if (z==x*y) { printf("Correct answer\n");  cor=cor+1;} }
	 printf("Correct answers: %d\nWrong answers: %d\n",cor,err);
	}

	system("pause");
	return 0;
}

	int GetRand(int min, int max)
{
  static int Init = 0;
  int rc;
  
  if (Init == 0)
  {
    srand(time(NULL));
    Init = 1;}

  rc = (rand() % (max - min + 1) + min);
  
  return (rc);
}

Thank you

[Narue]

So lets say you are given 10 seconds to answer the question and every correct answer adds you 10 seconds. How would i implement this?

The simplest approach would have you checking the difference of the time between the point where the question is displayed and the point where the user has submitted an answer. The benefit of this is it doesn't have to be real-time, which would require more complex concurrency techniques.

[JilMakias]

This is going to help you a lot.

I will google it for you :)