想输出随机的+5或+10的十次运算，计算最后分数的次数，为啥总是1

#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main()
{ int a,b,c,d,e,f,g,h,i,j,k,num1,x,n,m;
srand(time(NULL));
a=0,b=0,c=0,d=0,e=0,f=0,g=0,h=0,i=0,j=0,k=0,x=0;
for (n=1;n<100;n++)
{ for(m=0;m<10;m++)
{
num1=rand()*2/(RAND_MAX+1);
if (num1==0) x=x+5;
else x=x+10;}
if(x==50)a++;
if(x==55)b++;
if(x==60)c++;
if(x==65)d++;
if(x==70)e++;
if(x==75)f++;
if(x==80)g++;
if(x==85)h++;
if(x==90)i++;
if(x==95)j++;
if(x==100)k++;}
cout<<"a="<<a<<endl;
cout<<"b="<<b<<endl;
cout<<"c="<<c<<endl;
cout<<"d="<<d<<endl;
cout<<"e="<<e<<endl;
cout<<"f="<<f<<endl;
cout<<"g="<<g<<endl;
cout<<"h="<<h<<endl;
cout<<"i="<<i<<endl;
cout<<"j="<<j<<endl;
cout<<"k="<<k<<endl;
return 0;
}