Đề bài

Tính: a) \( - {\rm{ }}6,07 + 3,68\);                                             b) \(\dfrac{3}{5} + ( - {\rm{ }}4)\); c) \(1\dfrac{3}{5} - \dfrac{{ - 7}}{{11}}\);                                     d) \(\dfrac{{ - 7}}{{13}} + 0,6\); e) \( - {\rm{ 1,221}}{\rm{.}}\dfrac{2}{{ - 5}}\);                            g) \(\dfrac{{ - 17}}{7}:0,25\).

Lời giải chi tiết

a) \( - {\rm{ }}6,07 + 3,68 =-(6,07-3,68)=  - {\rm{ 2,39}}\);                              b) Do \(\dfrac{3}{5} = \dfrac{6}{{10}} = 0,6\) nên:\(\dfrac{3}{5} + ( - {\rm{ }}4) = \dfrac{3}{5} - 4 = 0,6 - 4 =-(4-0,6)=  - 3,4\);c) \(1\dfrac{3}{5} - \dfrac{{ - 7}}{{11}} = \dfrac{8}{5} + \dfrac{7}{{11}} = \dfrac{{88}}{{55}} + \dfrac{{35}}{{55}} = \dfrac{{123}}{{55}}\);                                d) \(\dfrac{{ - 7}}{{13}} + 0,6 = \dfrac{{ - 7}}{{13}} + \dfrac{6}{{10}} = \dfrac{{ - 70}}{{130}} + \dfrac{{78}}{{130}} = \dfrac{8}{{130}} = \dfrac{4}{{65}}\);e) Do \(\dfrac{2}{{ - 5}} = \dfrac{4}{{ - 10}} =- 0,4\) nên: \( - {\rm{ 1,221}}{\rm{.}}\dfrac{2}{{ - 5}} =  (- {\rm{ 1,221}}){\rm{.}}( - {\rm{ 0,4) = 0,4844}}\);       g) \(\dfrac{{ - 17}}{7}:0,25 = \dfrac{{ - 17}}{7}:\dfrac{1}{4} = \dfrac{{ - 17}}{7}.4 = \dfrac{{ - 68}}{7}\).