Question

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

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

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

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

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

Answer 2

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

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

Answer 3

Ta có:\(\frac{21}{11}x\frac{22}{17}x\frac{68}{63}=\frac{21x22x68}{11x17x63}=\frac{21x11x2x17x4}{11x17x21x3}=\frac{2x4}{3}\)=\(\frac{8}{3}\)

\(\frac{5}{14}x\frac{7}{13}x\frac{26}{25}=\frac{5x7x26}{14x13x25}=\frac{5x7x13x2}{7x2x13x5x5}=\frac{1}{5}\)

Mọi người tk cho mình nha. Mình cảm ơn nhiều ^-^

Answer 4

a) 

\(\frac{21}{11}\times\frac{22}{17}\times\frac{68}{63}\)

\(=\frac{21\times11\times2\times17\times4}{21\times3\times11\times17}\)

\(=\frac{8}{3}\)

b)

\(\frac{5}{14}\times\frac{7}{13}\times\frac{26}{25}\)

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

\(=\frac{1}{5}\)

Answer 5

a)\(\frac{21}{11}\times\frac{22}{17}\times\frac{68}{63}=\frac{21\times2\times11\times4\times17}{11\times17\times3\times21}=\frac{2\times4}{3}=\frac{8}{3}\)

b)\(\frac{5}{14}\times\frac{7}{13}\times\frac{26}{25}=\frac{5\times7\times2\times13}{5\times5\times2\times7\times13}=\frac{1}{5}\)

Answer 6

a) \(\frac{21}{11}.\frac{22}{17}.\frac{68}{63}=\frac{3.7.2.11.2.2.17}{11.17.3.3.7}=\frac{2^3}{3}=\frac{8}{3}\)

b) \(\frac{5}{14}.\frac{7}{13}.\frac{26}{25}=\frac{5.7.2.13}{2.7.13.5^2}=\frac{1}{5}\)

Answer 7

\(a)\frac{21}{11}\times\frac{22}{17}\times\frac{68}{63}\)

\(\Rightarrow\frac{7\times3\times11\times2\times17\times4}{11\times17\times7\times9}\)

\(\Rightarrow\frac{8}{3}\)

\(b)\frac{5}{14}\times\frac{7}{13}\times\frac{26}{25}\)

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

\(\Rightarrow\frac{1}{5}\)