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a, \(\frac{6}{7}.\frac{16}{15}.\frac{7}{6}.\frac{21}{32}=\frac{6}{7}.\frac{7}{6}.\frac{16}{15}.\frac{21}{32}\)=\(1.\frac{16}{15}.\frac{21}{32}=\frac{7}{5.2}=\frac{7}{10}\)
Phần b T2
c,\(\frac{7}{4}.\frac{11}{21}+\frac{11}{21}.\frac{5}{4}=\frac{11}{21}.\left(\frac{7}{4}+\frac{5}{4}\right)\)=\(\frac{11}{21}.3=\frac{11}{7}\)
\(a,\left(\frac{5}{7}+\frac{9}{7}\right)x\frac{21}{28}\)
\(C1:=\frac{14}{7}x\frac{21}{28}=\frac{3}{2}\)
\(C2:=\frac{5}{7}x\frac{21}{28}+\frac{9}{7}x\frac{21}{28}=\frac{15}{28}+\frac{27}{28}=\frac{3}{2}\)
\(b,\frac{4}{5}x\frac{13}{14}+\frac{13}{14}x\frac{1}{5}\)
\(C1:=\frac{26}{35}+\frac{13}{70}=\frac{13}{14}\)
\(C2:=\frac{13}{14}x\left(\frac{4}{5}+\frac{1}{5}\right)=\frac{13}{14}x1=\frac{13}{14}\)
học tốt ~~~
\(\left(2.8x-32\right):\frac{2}{3}=90\)
\(2.8\cdot x-32=90\cdot\frac{2}{3}\)
\(\frac{14}{5}x-32=60\)
\(\frac{14}{5}x=60+32\)
\(\frac{14}{5}x=92\)
\(x=\frac{230}{7}\)
B , c , d tương tự
3/7x25x35=3x25x35/7=3x25x5=375
Vậy theo mình thì chọn đáp án A
\(a,\frac{10}{21}×\frac{14}{25}=\frac{4}{15}\)
\(b,3\frac{1}{3}×\frac{12}{35}=\frac{10}{3}×\frac{12}{35}=\frac{8}{7}\)
\(c,\frac{7}{15}×\frac{11}{13}+\frac{7}{15}×\frac{2}{13}+\frac{8}{15}=\frac{7}{15}+\frac{8}{15}=1\)
\(d,\left(\frac{41}{75}+\frac{17}{10}\right)×\frac{80}{129}=\frac{4}{9}\)
7/21+3/21+14/21+25/21+125/21=174/21 rút gọn là 22/3 nhé
\(a,\frac{3}{5}\times\frac{7}{9}=\frac{3\times7}{5\times9}=\frac{3\times7}{5\times3\times3}=\frac{7}{5\times3}=\frac{7}{15}\)
\(b,\frac{9}{13}\times\frac{17}{18}=\frac{9\times17}{13\times18}=\frac{9\times17}{13\times2\times9}=\frac{17}{13\times2}=\frac{17}{26}\)
Câu c,d tương tự
Chọn C