a: \(\dfrac{2}{3}=\dfrac{2\cdot5}{3\cdot5}=\dfrac{10}{15};\dfrac{2}{5}=\dfrac{2\cdot3}{5\cdot3}=\dfrac{6}{15}\)
mà \(\dfrac{6}{15}< \dfrac{7}{15}< \dfrac{10}{15}\)
nên \(\dfrac{2}{5}< \dfrac{7}{15}< \dfrac{2}{3}\)
b: \(\dfrac{5}{6}=\dfrac{5\cdot2}{6\cdot2}=\dfrac{10}{12};\dfrac{4}{3}=\dfrac{4\cdot4}{3\cdot4}=\dfrac{16}{12};\dfrac{7}{12}=\dfrac{7}{12}\)
mà \(\dfrac{7}{12}< \dfrac{10}{12}< \dfrac{16}{12}\)
nên \(\dfrac{7}{12}< \dfrac{5}{6}< \dfrac{4}{3}\)
c: \(\dfrac{11}{20}=\dfrac{11}{20};\dfrac{1}{4}=\dfrac{1\cdot5}{4\cdot5}=\dfrac{5}{20};\dfrac{3}{5}=\dfrac{3\cdot4}{5\cdot4}=\dfrac{12}{20}\)
mà \(\dfrac{5}{20}< \dfrac{11}{20}< \dfrac{12}{20}\)
nên \(\dfrac{1}{4}< \dfrac{11}{20}< \dfrac{3}{5}\)
d: \(\dfrac{1}{2}=\dfrac{1\cdot7}{2\cdot7}=\dfrac{7}{14};\dfrac{3}{7}=\dfrac{3\cdot2}{7\cdot2}=\dfrac{6}{14};1=\dfrac{14}{14};\dfrac{15}{14}=\dfrac{15}{14}\)
mà \(\dfrac{6}{14}< \dfrac{7}{14}< \dfrac{14}{14}< \dfrac{15}{14}\)
nên \(\dfrac{3}{7}< \dfrac{1}{2}< 1< \dfrac{15}{14}\)
e: \(\dfrac{7}{24}=\dfrac{7}{24};\dfrac{5}{3}=\dfrac{5\cdot8}{3\cdot8}=\dfrac{40}{24};1=\dfrac{24}{24};\dfrac{9}{8}=\dfrac{9\cdot3}{8\cdot3}=\dfrac{27}{24}\)
mà \(\dfrac{7}{24}< \dfrac{24}{24}< \dfrac{27}{24}< \dfrac{40}{24}\)
nên \(\dfrac{7}{24}< 1< \dfrac{9}{8}< \dfrac{5}{3}\)
f: \(\dfrac{9}{18}=\dfrac{9}{18};1=\dfrac{18}{18};\dfrac{2}{3}=\dfrac{2\cdot6}{3\cdot6}=\dfrac{12}{18};\dfrac{1}{6}=\dfrac{1\cdot3}{3\cdot6}=\dfrac{3}{18}\)
mà \(\dfrac{3}{18}< \dfrac{9}{18}< \dfrac{12}{18}< \dfrac{18}{18}\)
nên \(\dfrac{1}{6}< \dfrac{9}{18}< \dfrac{2}{3}< 1\)
