Luyện tập - Bài 95 (SGK tập 1 - Trang 45)

Gửi bởi: Sách Giáo Khoa Vào 26 tháng 12 2018 lúc 11:14:47

Tính giá trị của các biểu thức :

\(A=-5,13:\left(5\dfrac{5}{28}-1\dfrac{8}{9}.1,25+1\dfrac{16}{63}\right)\)

\(B=\left(3\dfrac{1}{3}.1,9+19,5:4\dfrac{1}{3}\right)\left(\dfrac{62}{75}-\dfrac{4}{25}\right)\)

\(A=-5,13:\left(5\dfrac{5}{28}-1\dfrac{8}{9}.1,25+1\dfrac{16}{63}\right)\)

\(=-5,13:\left(\dfrac{145}{28}-\dfrac{17}{9}.\dfrac{125}{100}+\dfrac{79}{63}\right)\)

\(=-5,13:\left(\dfrac{145}{28}-\dfrac{17}{9}.\dfrac{5}{4}+\dfrac{79}{63}\right)\)

\(=-5,13:\left(\dfrac{145}{28}-\dfrac{85}{36}+\dfrac{79}{63}\right)\)

\(=-5,13:\dfrac{57}{14}=-5,13:\dfrac{15}{57}\)

\(=\dfrac{-71,82}{57}=1,26\)

Vậy \(A=1,26\)

\(B=\left(3\dfrac{1}{3}.1,9+19,5:4\dfrac{1}{3}\right).\left(\dfrac{62}{75}-\dfrac{4}{25}\right)\)

\(=\left(\dfrac{10}{3}.1,9+19,5:\dfrac{13}{3}\right).\left(\dfrac{62-12}{75}\right)\)

\(=\left(\dfrac{19}{3}+\dfrac{58,5}{13}\right).\dfrac{50}{75}\)

\(=\left(\dfrac{19}{3}+4,5\right).\dfrac{2}{3}\)

\(=\dfrac{32,5}{3}.\dfrac{2}{3}=\dfrac{65}{9}=7\dfrac{2}{9}\)

Vậy \(B=7\dfrac{2}{9}\)