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\(\frac{3}{8}\cdot\frac{4}{15}\cdot\frac{12}{9}=\frac{3.4.3.4}{2.4.3.5.3.3}=\frac{2}{15}\)
\(\dfrac{1}{3}-\dfrac{1}{5}=\dfrac{5}{15}-\dfrac{3}{15}=\dfrac{2}{15}\)
\(\dfrac{6}{7}-\dfrac{4}{9}=\dfrac{54}{63}-\dfrac{28}{63}=\dfrac{26}{63}\)
1, Rút gọn rồi tính
a) \(\frac{4}{5}+\frac{3}{15}\)
= \(\frac{4}{5}+\frac{1}{5}\)
= \(\frac{5}{5}\)
= \(1\)
b) \(\frac{2}{3}+\frac{32}{24}\)
= \(\frac{2}{3}+\frac{4}{3}\)
= \(\frac{6}{3}\)
= \(2\)
c) \(\frac{5}{6}+\frac{15}{18}\)
= \(\frac{5}{6}+\frac{5}{6}\)
= \(\frac{10}{6}\)
= \(\frac{5}{3}\)
2, Tính rồi rút gọn
a) \(\frac{8}{15}+\frac{2}{3}\)
= \(\frac{8}{15}+\frac{10}{15}\)
= \(\frac{18}{15}\)
= \(\frac{6}{5}\)
b) \(\frac{3}{7}+\frac{4}{8}\)
= \(\frac{24}{56}+\frac{28}{56}\)
= \(\frac{52}{56}\)
= \(\frac{13}{14}\)
\(\dfrac{7}{15}và\dfrac{5}{13}=\dfrac{7.13}{15.13}=\dfrac{91}{195};\dfrac{5}{13}=\dfrac{5.15}{13.15}=\dfrac{75}{195}\)
\(\dfrac{11}{12}và\dfrac{7}{48}=\dfrac{11.4}{12.4}=\dfrac{44}{48};\dfrac{7}{48}\)
\(\dfrac{24}{35}và\dfrac{21}{7}=\dfrac{24}{35};\dfrac{21}{7}=\dfrac{21.5}{7.5}=\dfrac{105}{35}\)
\(\dfrac{15}{16}và\dfrac{7}{8}=\dfrac{15}{16};\dfrac{7}{8}=\dfrac{7.2}{8.2}=\dfrac{14}{16}\)
\(\dfrac{4}{5}=\dfrac{12}{15}\\ \dfrac{15}{21}=\dfrac{5}{7}\\ \dfrac{3}{8}=\dfrac{12}{32}\\ \dfrac{36}{24}=\dfrac{6}{4}\)
4/5 = 12/15
15/21 = 5/7
3/8 =12/32
36/24 =6/4