Školjka

Odredi: $$\frac{1}{1\sqrt{2} + 2\sqrt{1}} + \frac{1}{2\sqrt{3} + 3\sqrt{2}} + \frac{1}{3\sqrt{4} + 4\sqrt{3}} + ... + \frac{1}{24\sqrt{25} + 25\sqrt{24}} = ?$$