Đáp án:
`a)``128/315`
`b)``8/65`
`c)``250/217`
`d)``7/10`
Giải thích các bước giải:
$a)\dfrac{1,28}{3,15}=\dfrac{\dfrac{128}{100}}{\dfrac{315}{100}}=\dfrac{\dfrac{128}{315}}{\dfrac{100}{100}}=\dfrac{128}{315}$
$b)\dfrac{\dfrac{2}{5}}{3\dfrac{1}{4}}=\dfrac{\dfrac{2}{5}}{\dfrac{13}{4}}=\dfrac{\dfrac{8}{20}}{\dfrac{65}{20}}=\dfrac{\dfrac{8}{65}}{\dfrac{20}{20}}=\dfrac{8}{65}$
$c)\dfrac{1\dfrac{3}{7}}{1,24}=\dfrac{\dfrac{10}{7}}{\dfrac{31}{25}}=\dfrac{\dfrac{250}{175}}{\dfrac{217}{175}}=\dfrac{250}{217}$
$d)\dfrac{2\dfrac{1}{5}}{3\dfrac{1}{7}}=\dfrac{\dfrac{11}{5}}{\dfrac{22}{7}}=\dfrac{\dfrac{77}{35}}{\dfrac{110}{35}}=\dfrac{\dfrac{77}{110}}{\dfrac{35}{35}}=\dfrac{77}{110}=\dfrac{7}{10}$
