Math Problem Solver

\[ 641 + 0.601 + 3 + 0.8 = \frac{645401}{1000} = 645.401 \]

The sum can be computed by rewriting each term over a common denominator, where the least common denominator of \(\frac{641}{1}\), \(\frac{601}{1000}\), \(\frac{3}{1}\), and \(\frac{8}{10}\) is \(1000\). \[ \begin{aligned} 641 + 0.601 + 3 + 0.8 &= \frac{641 \cdot 1000}{1 \cdot 1000} + \frac{601 \cdot 1}{1000 \cdot 1} + \frac{3 \cdot 1000}{1 \cdot 1000} + \frac{8 \cdot 100}{10 \cdot 100} \\ &= \frac{641000 + 601 + 3000 + 800}{1000} \\ &= \frac{645401}{1000} \end{aligned} \]