ta có : `1/4= 5/20 ; 2/5= 8/20`
`=> a/b` là :
`6/20` tức `3/10;7/20`
\(\dfrac{1}{4}< \dfrac{a}{b}< \dfrac{2}{5}\)
\(\dfrac{1}{4}=0,25\)
\(\dfrac{2}{5}=0,4\)
\(\dfrac{1}{3}=0,33\)
\(\Rightarrow\dfrac{1}{4}< \dfrac{1}{3}< \dfrac{2}{5}\)
VD: 3/10 (a=3 ; b=10)
7/20 (a=7; b=20)
17/50 (a=17; b=50)