Bài 1. (2,0 điểm) Tính hợp lí (nếu có thể). a) $1,3-4,5+3,7$ b) $(-0,35):7+7,5.0,1-0,7$ c) $\frac{5}{6}. (4\frac{1}{2}- 0,4) -0,1. (6\frac{1}{4}-3\frac{1}{3})$ 

$\text{a)}$ `1,3 - 4,5 + 3,7`

`= (1,3 + 3,7) - 4,5`

`= 5 - 4,5`

`= 0,5`

$\text{b)}$ `(-0,35) : 7 + 7,5 . 0,1 - 0,7`

`= (-0,05) + 0,75 - 0,7`

`= 0`

$\text{c)}$ `\frac{5}{6} . (4\frac{1}{2} - 0,4) - 0,1.(6\frac{1}{4} - 3\frac{1}{3})`

`= \frac{5}{6} . (\frac{9}{2} - \frac{2}{5}) - \frac{1}{10}.(\frac{25}{4} - \frac{10}{3})`

`= \frac{5}{6} . (\frac{45}{10} - \frac{4}{10}) - \frac{1}{10}.(\frac{75}{12} - \frac{40}{12})`

`= \frac{5}{6} . \frac{41}{10} - \frac{1}{10} . \frac{35}{12}`

`= \frac{205}{60} - \frac{35}{120}`

`= \frac{41}{12} - \frac{7}{24}`

`= \frac{82}{24} - \frac{7}{24}`

`= \frac{75}{24}`

`= \frac{25}{8}`