Question

Hãy so sánh 3 phân số sau bằng cách hợp lí nhất :

\(\frac{21}{25}\);  \(\frac{60}{81}\)và    \(\frac{19}{29}\)

Answer 1

\(\frac{21}{25}=\frac{49329}{58725}\)

\(\frac{60}{81}=\frac{43500}{58725}\)

\(\frac{19}{29}=\frac{38475}{58725}\)

\(\)vì \(\frac{49329}{58725}>\frac{43500}{58725}>\frac{38475}{58725}\)nên\(\frac{21}{25}>\frac{60}{81}>\frac{19}{29}\)

Answer 2

\(\frac{21}{25};\frac{60}{81};\frac{19}{29}\)

Ta có : \(\frac{60}{81}=\frac{60:3}{81:3}=\frac{20}{27}\); giữ nguyên \(\frac{21}{25};\frac{19}{29}\).

Vì \(\frac{21}{25}>\frac{20}{25}>\frac{20}{27}\)nên \(\frac{21}{25}>\frac{20}{27}\)

Vì  \(\frac{20}{27}>\frac{20}{29}>\frac{19}{29}\)nên \(\frac{20}{27}>\frac{19}{29}\). Vậy :

\(\frac{21}{25}>\frac{20}{27}>\frac{19}{29}\)hay  \(\frac{21}{25}>\frac{60}{81}>\frac{19}{29}\)