a) \(3\dfrac{9}{{10}} = \dfrac{{39}}{{10}}\;;\;\;2\dfrac{9}{{10}} = \dfrac{{29}}{{10}}.\) Mà \(\dfrac{{39}}{{10}} > {\rm{ }}\dfrac{{29}}{{10}}\)
Vậy : \(3\dfrac{9}{{10}} > {\rm{ }}2\dfrac{9}{{10}}\)
b) \(3\dfrac{4}{{10}} = \dfrac{{34}}{{10}}\;;\;\;3\dfrac{9}{{10}} = \dfrac{{39}}{{10}}.\) Mà \(\dfrac{{34}}{{10}} < \dfrac{{39}}{{10}}\)
Vậy : \(3\dfrac{4}{{10}} < {\rm{ }}3\dfrac{9}{{10}}\)
c) \(5\dfrac{1}{{10}} = \dfrac{{51}}{{10}}\;;\;\;2\dfrac{9}{{10}} = \dfrac{{29}}{{10}}.\) Mà \(\dfrac{{51}}{{10}} > {\rm{ }}\dfrac{{29}}{{10}}\)
Vậy : \(5\dfrac{1}{{10}} > {\rm{ }}2\dfrac{9}{{10}}\).
d) \(3\dfrac{4}{{10}} = \dfrac{{34}}{{10}} = \dfrac{{17}}{5}\;;\;\;3\dfrac{2}{5} = \dfrac{{17}}{5}\). Mà \(\dfrac{{17}}{5} = \dfrac{{17}}{5}\)
Vậy : \(3\dfrac{4}{{10}} = {\rm{ }}3\dfrac{2}{5}\)
