Đáp án và lời giải
Đáp án:A
Lời giải:Ta có: $\begin{array}{l} A = \frac{3}{5}:0,5 + \frac{3}{4}:0,25 = \frac{3}{5}:\frac{1}{2} + \frac{3}{4}:\frac{1}{4}\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad \;\;\; = \frac{3}{5} \times \frac{2}{1} + \frac{3}{4} \times \frac{4}{1}\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad \;\;\; = \frac{6}{5} + 3\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad \;\;\; = 4\frac{1}{5}\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad \;\;\; = 4,2. \end{array}$ Vậy khẳng định đúng là: A < 4,5.
