Câu 22 trang 11 Sách Bài Tập (SBT) Toán 7 tập 1

Tính:

$M = \left[ {\left( {{2 \over {193}} - {3 \over {386}}} \right).{{193} \over {17}} + {{33} \over {34}}} \right]:\left[ {\left( {{7 \over {2001}} + {{11} \over {4002}}} \right).{{2001} \over {25}} + {9 \over 2}} \right]$

Giải

$M = \left[ {\left( {{2 \over {193}} - {3 \over {386}}} \right).{{193} \over {17}} + {{33} \over {34}}} \right]:\left[ {\left( {{7 \over {2001}} + {{11} \over {4002}}} \right).{{2001} \over {25}} + {9 \over 2}} \right]$ 

$= \left[ {\left( {{4 \over {386}} - {3 \over {386}}} \right).{{193} \over {17}} + {{33} \over {34}}} \right]:\left[ {\left( {{{14} \over {4002}} + {{11} \over {4002}}} \right).{{2001} \over {25}} + {9 \over 2}} \right]$

$= \left[ {{1 \over {386}}.{{193} \over {17}} + {{33} \over {34}}} \right]:\left[ {{{25} \over {4002}}.{{2001} \over {25}} + {9 \over 2}} \right]$

$= \left( {{1 \over {34}} + {{33} \over {34}}} \right):\left( {{1 \over 2} + {9 \over 2}} \right) = 1:5 = {1 \over 5}$

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