Здравствуйте, Жиляев М. Ю..
Не знал, что есть, поэтому тоже набросал. Не проверял, но по идее должно работать

Приложение:
#include <math.h>

class Rational {
typedef unsigned int uint;

void reduce() {
if (denominator == 0) numerator = 0;
else {
uint top = ceil(sqrt(denominator));
for (uint i(2); i < top; i++)
if (((numerator % i) == 0) && ((denominator % i) == 0)) {
numerator /= i;
denominator /= i;
i = 2;
}
}
return;
}
public:
int numerator;
uint denominator;

Rational(int num = 0, uint den = 0) {
numerator = num;
denominator = den;
reduce();
}

Rational makeRational(int num, uint den) {
Rational v(num, den);
return v;
}

Rational operator +(Rational v) {
int num = numerator * v.denominator + denominator * v.numerator;
uint den = denominator * v.denominator;
return makeRational(num, den);
}

Rational operator -(Rational v) {
int num = numerator * v.denominator - denominator * v.numerator;
uint den = denominator * v.denominator;
return makeRational(num, den);
}

Rational operator *(Rational v) {
return makeRational(numerator * v.numerator,
denominator * v.denominator);
}

Rational operator /(Rational v) {
return makeRational(numerator * v.denominator,
denominator * v.numerator);
}
};