3. Tính:
Gửi bởi: Phạm Thọ Thái Dương Vào 1 tháng 7 2019 lúc 16:54:20
Câu hỏi
a) \(\frac{3}{4} + \frac{1}{2} + \frac{5}{8} = \)
b) \(\frac{5}{7} + \frac{9}{8} - \frac{{15}}{{28}} = \)
c) \(\frac{{11}}{{30}} - \frac{9}{{25}} \times \frac{{15}}{{27}} = \)
d) \(\frac{3}{4}:\frac{5}{8}:\frac{3}{{10}} = \)
Hướng dẫn giải
a) \(\frac{3}{4} + \frac{1}{2} + \frac{5}{8} = \frac{{6 + 4}}{8} + \frac{5}{8} = \frac{{10}}{8} + \frac{5}{8} = \frac{{15}}{8}\)
b)
\(\begin{array}{l}\frac{5}{7} + \frac{9}{8} - \frac{{15}}{{28}} = \frac{{40 + 63}}{{56}} - \frac{{15}}{{28}}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{103}}{{56}} - \frac{{15}}{{28}} = \frac{{103 - 30}}{{56}} = \frac{{73}}{{56}}\end{array}\)
c)
\(\begin{array}{l}\frac{{11}}{{30}} - \frac{9}{{25}} \times \frac{{15}}{{27}} = \frac{{11}}{{30}} - \frac{{1 \times 3}}{{5 \times 3}} = \frac{{11}}{{30}} - \frac{1}{5}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{11 - 6}}{{30}} = \frac{5}{{30}} = \frac{1}{6}\end{array}\)
d) \(\frac{3}{4}:\frac{5}{8}:\frac{3}{{10}} = \frac{3}{4} \times \frac{8}{5} \times \frac{{10}}{3} = 4\)
Update: 1 tháng 7 2019 lúc 16:54:20