[c++] invalid operands of types int and double to binary 'operator%'

After compiling the program I am getting below error

invalid operands of types int and double to binary 'operator%' at line 
"newnum1 = two % (double)10.0;"

Why is it so?

#include<iostream>
#include<math>
using namespace std;
int main()
{
    int num;
    double two = 1;
    double newnum, newnum1;
    newnum = newnum1 = 0;
    for(num = 1; num <= 50; num++)
    {

        two = two * 2;
    }
    newnum1 = two % (double)10.0;
    newnum = newnum + newnum1;
    cout << two << "\n";
    return 0;
}

Because % is only defined for integer types. That's the modulus operator.

5.6.2 of the standard:

The operands of * and / shall have arithmetic or enumeration type; the operands of % shall have integral or enumeration type. [...]

As Oli pointed out, you can use fmod(). Don't forget to include math.h.