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a)\(\dfrac{5}{7}+\dfrac{4}{9}=\dfrac{45}{63}+\dfrac{28}{63}=\dfrac{73}{63}\) ; \(\dfrac{9}{11}+\dfrac{3}{8}=\dfrac{72}{88}+\dfrac{33}{88}=\dfrac{105}{88}\)
\(\dfrac{4}{5}-\dfrac{2}{3}=\dfrac{12}{15}-\dfrac{10}{15}=\dfrac{2}{15}\); \(\dfrac{16}{25}-\dfrac{2}{5}=\dfrac{16}{25}-\dfrac{10}{25}=\dfrac{6}{25}\)
b)\(5+\dfrac{3}{5}=\dfrac{25}{5}+\dfrac{3}{5}=\dfrac{28}{5};10-\dfrac{9}{16}=\dfrac{160}{16}-\dfrac{9}{16}=\dfrac{151}{16}\)
\(\dfrac{2}{3}-\left(\dfrac{1}{6}+\dfrac{1}{8}\right)=\dfrac{2}{3}-\left(\dfrac{8}{48}+\dfrac{6}{48}\right)=\dfrac{2}{3}-\dfrac{14}{48}=\dfrac{32}{48}-\dfrac{14}{48}=\dfrac{3}{8}\)
\(a.\dfrac{3\times4\times7}{12\times8\times9}=\dfrac{3\times4\times7}{3\times4\times4\times2\times9}\\ =\dfrac{7}{4\times2\times9}=\dfrac{7}{72}\\ b.\dfrac{4\times5\times6}{12\times10\times8}=\dfrac{4\times5\times2\times3}{4\times3\times5\times2\times4\times2}=\dfrac{1}{8}\\ c.\dfrac{5\times6\times7}{12\times14\times15}=\dfrac{5\times6\times7}{2\times6\times7\times2\times5\times3}\\ =\dfrac{1}{2\times2\times3}=\dfrac{1}{12}\)
= (9/5 + 6/5) + 4/9 + 8/7 + 3/2 = 3 + (100/63 + 3/2) = 389/126 + 3 = 767/126
\(a.\left(\frac{6}{11}+\frac{5}{11}\right).\frac{3}{7}=1\cdot\frac{3}{7}=\frac{3}{7}b.\frac{3}{5}\cdot\frac{7}{9}+\frac{3}{5}\cdot\frac{2}{9}=\frac{3}{5}\cdot\left(\frac{7}{9}+\frac{2}{9}\right)=\frac{3}{5}\cdot1=\frac{3}{5}\)
\(\frac{1}{6}+\frac{5}{6}=\frac{6}{6}=1\)
\(\frac{25}{5}+\frac{2}{6}=\frac{150}{30}+\frac{10}{30}=\frac{160}{30}=\frac{32}{6}=\frac{16}{3}\)
\(\frac{12}{5}+\frac{6}{9}=\frac{108}{45}+\frac{30}{45}=\frac{138}{45}\)
12×7×275×6×7×9=(6×2)×7×(9×3)5×6×7×9
Rút gọn \(6 , 7 , 9\):
\(= \frac{5}{2 \times 3} = \frac{5}{6} .\)
✅ Kết quả: \(\frac{5}{6}\).
a)
\(\frac{3 \times 4 \times 7}{12 \times 8 \times 9}\)
\(\frac{84}{864} = \frac{84 \div 12}{864 \div 12} = \frac{7}{72} .\)
✅ Kết quả: \(\frac{7}{72}\).
b)
\(\frac{4 \times 5 \times 6}{12 \times 10 \times 8}\)
\(\frac{120}{960} = \frac{1}{8} .\)
✅ Kết quả: \(\frac{1}{8}\).
c)
\(\frac{5 \times 6 \times 7}{12 \times 14 \times 15}\)
\(\frac{210}{2520} = \frac{1}{12} .\)
✅ Kết quả: \(\frac{1}{12}\).
👉 Kết quả cuối cùng:
\(a,\left(\frac{6}{11}+\frac{5}{11}\right)\times\frac{3}{7}\)
Cách 1: \(\left(\frac{6}{11}+\frac{5}{11}\right)\times\frac{3}{7}=1\times\frac{3}{7}=\frac{10}{7}\)
Cách 2: \(\left(\frac{6}{11}+\frac{5}{11}\right)\times\frac{3}{7}=\frac{6}{11}\times\frac{3}{7}+\frac{5}{11}\times\frac{3}{7}=\frac{18}{77}+\frac{15}{77}=\frac{33}{77}=\frac{3}{7}\)
\(b,\frac{3}{5}\times\frac{7}{9}+\frac{3}{5}\times\frac{2}{9}\)
Cách 1: \(\frac{3}{5}\times\frac{7}{9}+\frac{3}{5}\times\frac{2}{9}=\frac{7}{15}+\frac{2}{15}=\frac{9}{15}\)
Cách 2: \(\frac{3}{5}\times\frac{7}{9}+\frac{3}{5}\times\frac{2}{9}=\frac{3}{5}\times1=\frac{3}{5}\)
P/s: Ý B có vấn đề thì phải
\(a,\left(\frac{6}{11}+\frac{5}{11}\right)x\frac{3}{7}\)
\(=\frac{11}{11}=1x\frac{3}{7}\)
\(=\frac{3}{7}\)
cach 2
\(\frac{6}{11}x\frac{3}{7}+\frac{5}{11}x\frac{3}{7}\)
\(=\frac{18}{77}+\frac{15}{77}\)
\(=\frac{33}{77}=\frac{3}{7}\)
\(b,\frac{3}{5}x\frac{7}{9}+\frac{3}{5}x\frac{2}{9}\)
\(=\frac{21}{45}+\frac{6}{45}\)
\(=\frac{27}{45}=\frac{3}{5}\)
cách 2 :
\(\frac{3}{5}x\left(\frac{7}{9}+\frac{2}{9}\right)\)
\(=\frac{3}{5}x\frac{9}{9}\)
\(=\frac{27}{45}=\frac{3}{5}\)
