Điền số hoặc phân số thích hợp vào chỗ chấm.
\(\frac{1}{5}\,\, + \,\frac{3}{{10}} = \,\,\frac{1}{2}\) Giải thích: \(\frac{1}{5}\,\, + \,\,........\,\, = \,\,\frac{1}{2}\) \(........\,\, = \,\,\frac{1}{2} - \frac{1}{5}\) \(........\,\, = \,\,\frac{{1 \times 5}}{{2 \times 5}} - \frac{{1 \times 2}}{{5 \times 2}}\) \(........\,\, = \,\,\frac{5}{{10}} - \frac{2}{{10}}\) \(........\,\, = \,\,\frac{3}{{10}}\) | \(\frac{{12}}{{15}}\,\, - \,\,\frac{1}{3}\,\, = \,\,\frac{7}{{15}}\) Giải thích: \(.........\,\, - \,\,\frac{1}{3}\,\, = \,\,\frac{7}{{15}}\) \(.........\,\,\,\, = \,\,\frac{7}{{15}} + \,\frac{1}{3}\) \(.........\,\,\,\, = \,\,\frac{7}{{15}} + \,\frac{{1 \times 5}}{{3 \times 5}}\) \(.........\,\,\,\, = \,\,\frac{7}{{15}} + \,\frac{5}{{15}}\) \(.........\,\,\,\, = \,\,\frac{{12}}{{15}}\) |
\(\frac{5}{{44}}\,\, \times \,\,\frac{{11}}{3}\,\, = \,\,\frac{5}{{12}}\) Giải thích: \(\frac{5}{{44}}\,\, \times \,\,\frac{{.......}}{3}\,\, = \,\,\frac{5}{{12}}\) \(\frac{{.......}}{3}\,\, = \,\,\frac{5}{{12}}:\frac{5}{{44}}\) \(\frac{{.......}}{3}\,\, = \,\,\frac{5}{{12}} \times \frac{{44}}{5}\) \(\frac{{.......}}{3}\,\, = \,\,\frac{{\not 5}}{{3 \times \not 4}} \times \frac{{\not 4 \times 11}}{{\not 5}}\) \(\frac{{.......}}{3}\,\, = \,\,\frac{{11}}{3}\) Vậy số cần điền là: 11 | \(\frac{5}{9}\,\,:\,\frac{{40}}{{27}}\, = \,\,\frac{3}{8}\) Giải thích: \(\frac{5}{9}\,\,:\,\,..........\,\, = \,\,\frac{3}{8}\) \(\,..........\,\, = \,\,\frac{5}{9}\,\,:\,\frac{3}{8}\) \(\,..........\,\, = \,\,\frac{{40}}{{27}}\,\,\) |