Question

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Tính bằng cách thuận tiện nhất:

a) \(\frac{21}{11}x\frac{22}{17}x\frac{68}{63}\)                                                        b) \(\frac{5}{14}x\frac{7}{13}x\frac{26}{25}\)

Answer 1

[Đức Phạm]

\(\frac{21}{11}\times\frac{22}{17}\times\frac{68}{63}=\frac{21\times22\times68}{11\times17\times63}\)

\(=\frac{7\times3\times11\times2\times17\times4}{11\times17\times7\times9}=\frac{24}{9}=\frac{8}{3}\)

\(\frac{5}{14}\times\frac{7}{13}\times\frac{26}{25}=\frac{5\times7\times26}{14\times13\times25}\)

\(=\frac{5\times7\times2\times13}{7\times2\times13\times5\times5}=\frac{1}{5}\)

Answer 2

[Kaori Miyazono]

\(\frac{21}{11}.\frac{22}{17}.\frac{68}{63}=\frac{21.22.68}{11.17.63}=\frac{21.2.11.4.17}{11.17.21.3}=\frac{\left(17.11.21\right).2.4}{\left(11.17.21\right).3}=\frac{2.4}{3}=\frac{8}{3}\)

\(\frac{5}{14}.\frac{7}{13}.\frac{26}{25}=\frac{5.7.26}{14.13.25}=\frac{5.7.13.2}{2.7.13.4.5}=\frac{\left(5.7.13.2\right)}{\left(5.7.13.2\right).5}=\frac{1}{5}\)