Tính \(\dfrac{{ - 5}}{8} + \dfrac{{ - 7}}{{20}}\)
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23 tháng 3 2021 lúc 20:14
Tính nhanh:
\(A=\dfrac{5}{13}=\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
Ta có: \(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)
\(=1-1+\dfrac{-5}{7}\)
\(=\dfrac{-5}{7}\)
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\(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}=(\dfrac{5}{13}+\dfrac{8}{13})+(\dfrac{-20}{41}+\dfrac{-21}{41})+(\dfrac{-5}{7})=1+\left(-1\right)+\dfrac{-5}{7}=0+\dfrac{-5}{7}=\dfrac{-5}{7}\)
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Tính nhanh :
\(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41};B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)
2 tháng 2 2022 lúc 17:34
Tính một cách hợp lí :
\(a,A=\dfrac{9}{11}+\dfrac{5}{7}+\dfrac{20}{11}+\dfrac{8}{13}+\dfrac{2}{7}\)
\(=\left(\dfrac{9}{11}+\dfrac{20}{11}\right)+\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{8}{13}\\ =\dfrac{29}{11}+1+\dfrac{8}{13}\)
Biết đến đó thôi sorry:<
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=(9/11+20/11)+(5/7+2/7)+8/13
=29/11+1+8/13
=377/143+1/143/143+88/143
=608/143
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=(9/11+20/11)+(5/7+2/7)+8/13
=29/11+1+8/13
=377/143+143/143+88/143
=608/143
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Thực hiện phép tính (hợp lí nếu có thể):
a) 13dfrac{2}{7} : (dfrac{-8}{9}) + 2dfrac{5}{7} : (dfrac{-8}{9})
b) (dfrac{-6}{11}) . dfrac{7}{10} . (dfrac{11}{-6}) . (-20)
c) (-1dfrac{1}{2}) : dfrac{3}{4} . (-4dfrac{1}{2})
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Thực hiện phép tính (hợp lí nếu có thể):
a) \(13\dfrac{2}{7}\) : (\(\dfrac{-8}{9}\)) + \(2\dfrac{5}{7}\) : (\(\dfrac{-8}{9}\))
b) (\(\dfrac{-6}{11}\)) . \(\dfrac{7}{10}\) . (\(\dfrac{11}{-6}\)) . (-20)
c) (\(-1\dfrac{1}{2}\)) : \(\dfrac{3}{4}\) . (\(-4\dfrac{1}{2}\))
a) \(=\left(13\dfrac{2}{7}+2\dfrac{5}{7}\right):\left(-\dfrac{8}{9}\right)\)
\(=16:\dfrac{-8}{9}=\dfrac{-8\cdot\left(-2\right)\cdot9}{-8}=-18\)
b)
\(=\left(\dfrac{-6}{11}\cdot\dfrac{11}{-6}\right)\cdot\dfrac{7\cdot10\cdot\left(-2\right)}{10}\)
\(=-14\)
c) \(=\dfrac{-1}{2}\cdot\dfrac{4}{3}\cdot\dfrac{-7}{2}\)
\(=\dfrac{-1\cdot2\cdot2\cdot\left(-7\right)}{2\cdot3\cdot2}=\dfrac{7}{3}\)
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17 tháng 2 2023 lúc 18:30
Phân số lớn nhất trong các phân số \(\dfrac{1}{5}\);\(\dfrac{5}{8}\);\(\dfrac{7}{20}\);\(\dfrac{19}{40}\) là:
A. \(\dfrac{1}{5}\) B. \(\dfrac{5}{8}\) C. \(\dfrac{7}{20}\) D. \(\dfrac{19}{20}\)
ta có :
`1/5=(1xx8)/(5xx8)=8/40`
`5/8=(5xx5)/(8xx5)=25/40`
`7/20=(7xx2)/(20xx2)=14/40`
`19/40=19/40`
`->5/8` lớn nhất
`=>B`
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help me ạ! Mình sẽ tick ah!~
Thanks
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SGK Kết nối tri thức với cuộc sống - Trang 57
23 tháng 8 2023 lúc 22:52
Số?a) dfrac{2}{5}dfrac{2times3}{5times3}dfrac{?}{?} dfrac{4}{7}dfrac{4times2}{7times2}dfrac{?}{?} dfrac{13}{54}dfrac{13times3}{54times3}dfrac{?}{?}b) dfrac{8}{20}dfrac{8:4}{20:4}dfrac{?}{?} dfrac{10}{16}dfrac{10:2}{16:2}dfrac{?}{?} dfrac{25}{65}dfrac{25:5}{65:5}dfrac{?}{?}
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Số?
a) \(\dfrac{2}{5}=\dfrac{2\times3}{5\times3}=\dfrac{?}{?}\) \(\dfrac{4}{7}=\dfrac{4\times2}{7\times2}=\dfrac{?}{?}\) \(\dfrac{13}{54}=\dfrac{13\times3}{54\times3}=\dfrac{?}{?}\)
b) \(\dfrac{8}{20}=\dfrac{8:4}{20:4}=\dfrac{?}{?}\) \(\dfrac{10}{16}=\dfrac{10:2}{16:2}=\dfrac{?}{?}\) \(\dfrac{25}{65}=\dfrac{25:5}{65:5}=\dfrac{?}{?}\)
a) \(\dfrac{2}{5}=\dfrac{2\times3}{5\times3}=\dfrac{6}{15}=\dfrac{2}{5}\)
\(\dfrac{4}{7}=\dfrac{4\times2}{7\times2}=\dfrac{8}{14}=\dfrac{4}{7}\)
\(\dfrac{13}{54}=\dfrac{13\times3}{54\times3}=\dfrac{39}{162}=\dfrac{13}{54}\)
b) \(\dfrac{8}{20}=\dfrac{8:4}{20:4}=\dfrac{2}{5}\)
\(\dfrac{10}{16}=\dfrac{10:2}{16:2}=\dfrac{5}{8}\)
\(\dfrac{25}{65}=\dfrac{25:5}{65:5}=\dfrac{5}{13}\)
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Thực hiện phép tính (hợp lí nếu có thể):
a) (dfrac{-6}{11}) . dfrac{7}{10} . dfrac{11}{-6} . (-20)
b) (-1dfrac{1}{2}) : dfrac{3}{4} . -4dfrac{1}{2})
c) 13dfrac{2}{7} : (dfrac{-8}{9}) + 2dfrac{5}{7} : (dfrac{-8}{9})
Đọc tiếp
Thực hiện phép tính (hợp lí nếu có thể):
a) (\(\dfrac{-6}{11}\)) . \(\dfrac{7}{10}\) . \(\dfrac{11}{-6}\) . (-20)
b) (\(-1\dfrac{1}{2}\)) : \(\dfrac{3}{4}\) . \(-4\dfrac{1}{2}\))
c) \(13\dfrac{2}{7}\) : (\(\dfrac{-8}{9}\)) + \(2\dfrac{5}{7}\) : (\(\dfrac{-8}{9}\))
\(a.\left[-\dfrac{6}{11}.\dfrac{11}{-6}\right].\dfrac{7}{10}.\left(-20\right)=1.7.\left(-2\right)=-14\)
\(b.\dfrac{-1}{2}:\dfrac{3}{4}.\dfrac{-7}{2}=\dfrac{7}{4}:\dfrac{3}{4}=\dfrac{7}{3}\)
\(c.\dfrac{93}{7}:-\dfrac{8}{9}+\dfrac{19}{7}:\dfrac{-8}{9}=\left(\dfrac{93}{7}+\dfrac{19}{7}\right):-\dfrac{8}{9}=\dfrac{-9}{8}.\dfrac{112}{7}=-18\)
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5. dfrac{-3}{7} + dfrac{5}{13} + dfrac{-4}{12}6. dfrac{-5}{21} + dfrac{-2}{21} + dfrac{8}{24}7. dfrac{5}{13} + dfrac{-5}{7} + dfrac{-20}{41} + dfrac{8}{13} + dfrac{-21}{41}Giúp tớ với ạ🥺👉🏻👈🏻 Tớ cảm ơn nhiều🥰
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5. \(\dfrac{-3}{7}\) + \(\dfrac{5}{13}\) + \(\dfrac{-4}{12}\)
6. \(\dfrac{-5}{21}\) + \(\dfrac{-2}{21}\) + \(\dfrac{8}{24}\)
7. \(\dfrac{5}{13}\) + \(\dfrac{-5}{7}\) + \(\dfrac{-20}{41}\) + \(\dfrac{8}{13}\) + \(\dfrac{-21}{41}\)
Giúp tớ với ạ🥺👉🏻👈🏻 Tớ cảm ơn nhiều🥰
5.\(-\dfrac{3}{7}+\dfrac{5}{13}+\dfrac{-4}{12}=-\dfrac{103}{273}\)
b.\(-\dfrac{5}{21}+\dfrac{-2}{21}+\dfrac{8}{24}=\dfrac{-5-2}{21}+\dfrac{8}{24}=-\dfrac{7}{21}+\dfrac{8}{24}=-\dfrac{1}{3}+\dfrac{8}{24}=0\)
c.\(\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+-\dfrac{5}{7}=1-1-\dfrac{5}{7}=-\dfrac{5}{7}\)
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a)\(\dfrac{3}{5}\)+\(\dfrac{17}{21}\)*\(\dfrac{17}{21}\)+\(\dfrac{3}{5}\)
b)\(\dfrac{15}{8}\):\(\dfrac{5}{20}\)-\(\dfrac{7}{8}\):\(\dfrac{1}{4}\)
a)\(\left(\dfrac{3}{5}+\dfrac{17}{21}\right)^2\)
b)4
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