Giải sgk toán 6 tập 2: bài tập 110 trang 49

\(A = 11{3 \over {13}} - \left( {2{4 \over 7} + 5{3 \over {13}}} \right) \)

\(= \left( {11{3 \over {13}} - 5{5 \over {13}}} \right) - 2{4 \over 7}\)

\( = 6 - 2{4 \over 7} \)

\(= 5{7 \over 7} - 2{4 \over 7} \)

\(=3\frac{3}{7}\)

\(B = \left( {6{4 \over 9} + 3{7 \over {11}}} \right) - 4{4 \over 9} \)

\(= \left( {6{4 \over 9} - 4{4 \over 9}} \right) + 3{7 \over {11}}\)

\( = 2 + {{40} \over {11}} \)

\(=2+3\frac{7}{11}= 5{7 \over {11}}\)

\(C = {{ - 5} \over 7}.{2 \over {11}} + {{ - 5} \over 7}.{9 \over {11}} + 1{5 \over 7} \)

\(= {{ - 5} \over 7}\left( {{2 \over {11}} + {9 \over {11}}} \right) + 1{5 \over 7}\)

\( = {{ - 5} \over 7} + 1{5 \over 7} \)

\(= {{ - 5} \over 7} +1+{5 \over 7} \)

\(= {{ - 5} \over 7} +{5 \over 7}+1 =1\)

\(D = 0,7.2{2 \over 3}.20.0,375.{5 \over {28}} \)

\(= {7 \over {10}}.{8 \over 3}.20.{{375} \over {1000}}.{5 \over {28}} \)

\(= {{70} \over {28}} = {5 \over 2}\)

\(E = \left( { - 6,17 + 3{5 \over 9} - 2{{36} \over {97}}} \right).\left( {{1 \over 3} - 0,25 - {1 \over {12}}} \right)\)

\(=\left( { - 6,17 + 3{5 \over 9} - 2{{36} \over {97}}} \right).\left( {{4 \over {12}} - \frac{3}{12} - {1 \over {12}}} \right)\)

\(=\left( { - 6,17 + 3{5 \over 9} - 2{{36} \over {97}}} \right).0=0\)