Câu 138 trang 33 Sách Bài Tập (SBT) Toán lớp 7 tập 1

Tính

\(E = {{\left( {13{1 \over 4} - 2{5 \over {27}} - 10{5 \over 6}} \right).230{1 \over {25}} + 46{3 \over 4}} \over {\left( {1{3 \over 7} + {{10} \over 3}} \right):\left( {12{1 \over 3} - 14{2 \over 7}} \right)}}\) 

Giải

\(E = {{\left( {13{1 \over 4} - 2{5 \over {27}} - 10{5 \over 6}} \right).230{1 \over {25}} + 46{3 \over 4}} \over {\left( {1{3 \over 7} + {{10} \over 3}} \right):\left( {12{1 \over 3} - 14{2 \over 7}} \right)}}\) 

\(\eqalign{
& = {{\left( {13 - 2 - 10 + {1 \over 4} - {5 \over {27}} - {5 \over 6}} \right).{{5751} \over {25}} + {{187} \over 4}} \over {\left( {{{30} \over {21}} + {{70} \over {21}}} \right):\left( {{{259} \over {21}} - {{300} \over {21}}} \right)}} \cr
& = {{\left( {1 + {{27 - 20 - 90} \over {108}}} \right).{{5751} \over {25}} + {{187} \over 4}} \over {{{100} \over {21}}:{{ - 41} \over {21}}}} \cr} \)

\(\eqalign{
& = {{\left( {{{108} \over {108}} - {{83} \over {108}}} \right).{{5751} \over {25}} + {{187} \over 4}} \over {{{100} \over {21}}.{{ - 21} \over {41}}}} \cr
& = {{{{25} \over {108}}.{{5751} \over {25}} + {{187} \over 4}} \over {{{ - 100} \over {41}}}} \cr
& = \left( {{{213} \over 4} + {{187} \over 4}} \right).{{ - 41} \over {100}} = 100.{{ - 41} \over {100}} \cr} \)

= -41

Sachbaitap.com