adding objects data of a class in C++

adding objects data of a class in C++

I was writing a program for adding 2 objects of a class.
//program for adding 2 objects data of same class
#include<iostream>
using namespace std;
class distances
{ private:
int feet;
float inches;
public:
distances() //constructor
{
feet=0;
inches=0.0;
}
distances(int f,float i) //constructor
{
feet=f;
inches=i;
}
void get_data() //taking value
{
cout<<"Enter the distance in feet and inches :: "<<"\n";
cin>>feet>>inches;
}
void show_data() //showing data
{
cout<<"The distance in feet is ::"<<feet <<" and in inches is ::
"<<inches;
}
void add(distances d1 ,distances d2); //adding to objects
};
void distances::add( distances d1,distances d2)
{
inches=d1.inches+d2.inches;
feet=0;
while(inches>=12)
{
inches=inches-12;
++feet;
}
feet+=d1.feet+d2.feet;
}
void main()
{distances d1,d2,d3;
d1.get_data();
d2.get_data();
d3.add(d1,d2);
d3.show_data();
getch();
}
My program worked fine but my sir told that my approach of adding 2
objects was wrong ,although he didn't tell why.He told me that my approach
won't work when I will add more objects. I don't know why my approach was
wrong.My friend told me that my problem might be in the line
d3.add(d1,d2);
Is that true?
My second problem was that when I used class name,function name and
constructor name as distance instead of distances then following error was
coming
1>c:\users\abc\documents\visual studio
2010\projects\pass\pass\pass.cpp(47): error C2872: 'distance' : ambiguous
symbol
1> could be 'c:\users\abc\documents\visual studio
2010\projects\pass\pass\pass.cpp(6) : distance'
1> or 'c:\program files (x86)\microsoft visual studio
10.0\vc\include\xutility(899) : iterator_traits<_Iter>::difference_type
std::distance(_InIt,_InIt)'