程序代码：

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

int main()
{
    int a,b,c;
    time_t start,end;
    start=time(0);
    a=rand() % 100;
    b=rand() % 100;
    printf("%d + %d = ",a,b);
    scanf("%d",&c);
    if(c==a+b)
    {
        printf("\nyou did right"); 
    }
    else
    {
        printf("\nyou did wrong");
    }
    
    end=time(0);
    printf("\ntime: %.2f seconds.",difftime(end,start));
    
    return 0;
}