When should a private method take the public route to access private data?

When should a private method take the public route to access private data? For example, if I had this immutable 'multiplier' class (a bit contrived, I know):

class Multiplier {
public:
    Multiplier(int a, int b) : a(a), b(b) { }
    int getA() const { return a; }
    int getB() const { return b; }
    int getProduct() const { /* ??? */ }
private:
    int a, b;
};

There are two ways I could implement getProduct:

    int getProduct() const { return a * b; }

or

    int getProduct() const { return getA() * getB(); }

Because the intention here is to use the value of a, i.e. to get a, using getA() to implement getProduct() seems cleaner to me. I would prefer to avoid using a unless I had to modify it. My concern is that I don't often see code written this way, in my experience a * b would be a more common implementation than getA() * getB().

Should private methods ever use the public way when they can access something directly?