(1,5 điểm) Thực hiện phép tính (tính hợp lý nếu có thể) :
a) $\dfrac{-2}{7}+\dfrac{2}{7}:\dfrac{3}{5}$
b) $\dfrac{-8}{19}+\dfrac{-4}{21}-\dfrac{17}{21}+\dfrac{27}{19}$
c) $\dfrac{6}{5}.\dfrac{3}{13}-\dfrac{6}{5}.\dfrac{16}{13}$
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Thực hiện phép tính (bằng cách hợp lý nếu có thể)
a) \(1\dfrac{4}{23}+\dfrac{5}{21}-\dfrac{4}{23}+0,5+\dfrac{16}{21}\)
b) \(\dfrac{3}{7}.19\dfrac{1}{3}-\dfrac{3}{7}.33\dfrac{1}{3}\)
c) \(9.\left(-\dfrac{1}{3}\right)^3+\dfrac{1}{3}\)
d) \(15\dfrac{1}{4}:\left(-\dfrac{5}{7}\right)-25\dfrac{1}{4}\left(-\dfrac{5}{7}\right)\)
bài 3 thực hiện phép tínhadfrac{5}{8}+dfrac{3}{17}+dfrac{4}{18}+dfrac{20}{-17}+dfrac{-2}{9}+dfrac{21}{56}bleft(dfrac{9}{16}+dfrac{8}{-27}right)+left(1+dfrac{7}{16}+dfrac{-19}{27}right)cleft(dfrac{13}{5}+dfrac{7}{16}right)+left(dfrac{-15}{16}+dfrac{6}{15}right) d left(6-2dfrac{4}{5}right).3dfrac{1}{8}-1dfrac{3}{5}:dfrac{1}{4}
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bài 3 thực hiện phép tính
a\(\dfrac{5}{8}+\dfrac{3}{17}+\dfrac{4}{18}+\dfrac{20}{-17}+\dfrac{-2}{9}+\dfrac{21}{56}\)
b\(\left(\dfrac{9}{16}+\dfrac{8}{-27}\right)+\left(1+\dfrac{7}{16}+\dfrac{-19}{27}\right)\)
c\(\left(\dfrac{13}{5}+\dfrac{7}{16}\right)+\left(\dfrac{-15}{16}+\dfrac{6}{15}\right)\) d \(\left(6-2\dfrac{4}{5}\right).3\dfrac{1}{8}-1\dfrac{3}{5}:\dfrac{1}{4}\)
a) Ta có: \(\dfrac{5}{8}+\dfrac{3}{17}+\dfrac{4}{18}+\dfrac{20}{-17}+\dfrac{-2}{9}+\dfrac{21}{56}\)
\(=\left(\dfrac{3}{17}-\dfrac{20}{17}\right)+\left(\dfrac{2}{9}-\dfrac{2}{9}\right)+\left(\dfrac{5}{8}+\dfrac{3}{8}\right)\)
\(=-1+1=0\)
b) Ta có: \(\left(\dfrac{9}{16}+\dfrac{8}{-27}\right)+\left(1+\dfrac{7}{16}+\dfrac{-19}{27}\right)\)
\(=\left(\dfrac{9}{16}+\dfrac{7}{16}\right)+\left(\dfrac{-8}{27}-\dfrac{19}{27}\right)+1\)
=1-1+1=1
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Thực hiện phép tính (tính hợp lí nếu có thể):
a) \(\dfrac{5}{3}.\dfrac{7}{25}+\dfrac{5}{3}.\dfrac{21}{25}-\dfrac{5}{3}.\dfrac{7}{25}\) b) 250% + \(19\dfrac{3}{11}.\dfrac{7}{26}-6\dfrac{3}{11}.\dfrac{7}{26}\)
\(\dfrac{5}{3}\cdot\dfrac{7}{25}+\dfrac{5}{3}\cdot\dfrac{21}{25}-\dfrac{5}{3}\cdot\dfrac{7}{25}\)
\(=\dfrac{5}{3}\cdot\left(\dfrac{7.}{25}+\dfrac{21}{25}-\dfrac{7}{25}\right)\)
\(=\dfrac{5}{3}\cdot\dfrac{21}{25}=\dfrac{7}{5}\)
b) \(250\%+19\dfrac{3}{11}\cdot\dfrac{7}{26}-6\dfrac{3}{11}\cdot\dfrac{7}{26}\)
\(=\dfrac{5}{2}+\dfrac{212}{11}\cdot\dfrac{7}{26}-\dfrac{69}{11}\cdot\dfrac{7}{26}\)
\(=\dfrac{7}{26}\cdot\left(\dfrac{212}{11}-\dfrac{69}{11}\right)+\dfrac{5}{2}\)
\(=\dfrac{7}{26}\cdot13+\dfrac{5}{2}\)
\(=\dfrac{7}{2}+\dfrac{5}{2}\)
\(=\dfrac{12}{2}=6\)
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Thực hiện phép tính hợp lý (nếu có thể) :
a) (31dfrac{6}{13} + 5dfrac{9}{41} ) - 36dfrac{6}{13}
b) dfrac{5}{3} +( dfrac{-2}{7} ) - (-1,2)
c) 0,25 + dfrac{3}{5} - (dfrac{1}{8} - dfrac{2}{5} + 1dfrac{1}{4} )
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Thực hiện phép tính hợp lý (nếu có thể) :
a) (\(31\dfrac{6}{13}\) + \(5\dfrac{9}{41}\) ) - \(36\dfrac{6}{13}\)
b) \(\dfrac{5}{3}\) +( \(\dfrac{-2}{7}\) ) - (-1,2)
c) 0,25 + \(\dfrac{3}{5}\) - (\(\dfrac{1}{8}\) - \(\dfrac{2}{5}\) + \(1\dfrac{1}{4}\) )
\(a,\left(31\dfrac{6}{13}+5\dfrac{9}{41}\right)-36\dfrac{6}{13}\\ =\left(31-36\right)+\left(\dfrac{6}{13}-\dfrac{6}{13}\right)+5\dfrac{9}{41}\\ =-5+0+5\dfrac{9}{41}\\ =\left(-5+5\right)+\dfrac{9}{41}=\dfrac{9}{41}\)
\(b,\dfrac{5}{3}+\left(-\dfrac{2}{7}\right)-\left(-1,2\right)\\ =\dfrac{5}{3}-\dfrac{2}{7}+\dfrac{6}{5}\\ =\dfrac{5.35-2.15+6.21}{105}=\dfrac{271}{105}\\ c,0,25+\dfrac{3}{5}-\left(\dfrac{1}{8}-\dfrac{2}{5}+1\dfrac{1}{4}\right)=\dfrac{1}{4}+\dfrac{3}{5}-\dfrac{1}{8}+\dfrac{2}{5}-1\dfrac{1}{4}\\ =\left(-1\dfrac{1}{4}+\dfrac{1}{4}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)-\dfrac{1}{8}=-1+1-\dfrac{1}{8}=-\dfrac{1}{8}\)
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a) (31 6/13 + 5 9/41) - 36 6/13
= 409/13 + 214/41 - 474/13
= (409/13 - 474/13) + 214/41
= -5 + 214/41
= 9/41
b) 5/3 + (-2/7) - (-1,2)
= 5/3 - 2/7 + 6/5
= 29/21 + 6/5
= 271/105
c) 0,25 + 3/5 - (1/8 - 2/5 + 1 1/4)
= 1/4 + 3/5 - 1/8 + 2/5 - 5/4
= (1/4 - 5/4) + (3/5 + 2/5) - 1/8
= -1 + 1 - 1/8
= -1/8
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Thực hiện phép tính (tính nhanh nếu có thể)
a) -19+7+9+19
b) \(11\dfrac{3}{13}-\left(2\dfrac{4}{7}+5\dfrac{3}{13}\right)\)
c) \(\dfrac{2}{7}.5\dfrac{1}{4}-\dfrac{2}{7}.3\dfrac{1}{4}\)
a: =9+7=16
b: =11+3/13-2-4/7-5-3/13
=4-4/7
=28/7-4/7=24/7
c: =2/7(5+1/4-3-1/4)=2/7x2=4/7
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Thực hiện phép tính (tính hợp lý nếu có thể): \(\dfrac{-5}{6}.\dfrac{4}{19}+\dfrac{-7}{12}.\dfrac{4}{19}-\dfrac{40}{57}\)
\(=\dfrac{4}{19}\left(\dfrac{-5}{6}-\dfrac{7}{12}-\dfrac{10}{3}\right)\)
\(=\dfrac{4}{19}\cdot\left(\dfrac{-10-7-40}{12}\right)=\dfrac{4}{19}\cdot\dfrac{-57}{12}=-\dfrac{3}{3}=-1\)
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=\(\dfrac{4}{19}.\left(-\dfrac{5}{6}+-\dfrac{7}{12}\right)-\dfrac{40}{57}\)
=\(-\dfrac{4}{19}-\dfrac{40}{57}\)
=\(-\dfrac{52}{57}\)
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Thực hiện phép tính (tính hợp lý nếu có thể): a) dfrac{5}{9}.dfrac{7}{13}+dfrac{5}{9}.dfrac{8}{13}-dfrac{5}{13}.dfrac{2}{9} b) 12dfrac{5}{14}-left(3dfrac{5}{7}+5dfrac{5}{14}right) c)dfrac{-2}{5}+dfrac{7}{11}+dfrac{-11}{10}+dfrac{7}{-11} d) dfrac{1}{2}+dfrac{-2}{3}+dfrac{1}{6}+dfrac{-2}{5}
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Thực hiện phép tính (tính hợp lý nếu có thể):
a) \(\dfrac{5}{9}.\dfrac{7}{13}+\dfrac{5}{9}.\dfrac{8}{13}-\dfrac{5}{13}.\dfrac{2}{9}\) b) \(12\dfrac{5}{14}-\left(3\dfrac{5}{7}+5\dfrac{5}{14}\right)\)
c)\(\dfrac{-2}{5}+\dfrac{7}{11}+\dfrac{-11}{10}+\dfrac{7}{-11}\) d) \(\dfrac{1}{2}+\dfrac{-2}{3}+\dfrac{1}{6}+\dfrac{-2}{5}\)
b: =12+5/14-3-5/7-5-5/14
=4-5/7
=28/7-5/7=23/7
c: =(-2/5-11/10)+(7/11-7/11)
=-4/10-11/10=-15/10=-3/2
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\(a,\dfrac{5}{9}\cdot\dfrac{7}{13}+\dfrac{5}{9}\cdot\dfrac{8}{13}-\dfrac{5}{13}\cdot\dfrac{2}{9}\)
\(=\dfrac{5}{9}\cdot\dfrac{7}{13}+\dfrac{5}{9}\cdot\dfrac{8}{13}-\dfrac{2}{13}\cdot\dfrac{5}{9}\)
\(=\dfrac{5}{9}\cdot\left(\dfrac{7}{13}+\dfrac{8}{13}-\dfrac{2}{13}\right)\)
\(=\dfrac{5}{9}\cdot\dfrac{14}{13}\)
\(=\dfrac{70}{117}\)
\(d,\dfrac{1}{2}+\dfrac{-2}{3}+\dfrac{1}{6}+\dfrac{-2}{5}\)
\(=\left(\dfrac{1}{2}+\dfrac{-2}{3}+\dfrac{1}{6}\right)+\dfrac{-2}{5}\)
\(=0+\dfrac{-2}{5}\)
\(=\dfrac{-2}{5}\)
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Tính hợp lý nếu có thể:
a) \(\dfrac{2}{9}+\dfrac{-3}{10}+\dfrac{-7}{10}\)
b) \(\dfrac{-11}{6}+\dfrac{2}{5}+\dfrac{-1}{6}\)
c) \(\dfrac{27}{13}-\dfrac{106}{111}+\dfrac{-5}{111}\)
d) \(\dfrac{12}{11}-\dfrac{-7}{19}+\dfrac{12}{19}\)
a, \(=\dfrac{2}{9}-\dfrac{10}{10}=\dfrac{2}{9}-1=-\dfrac{7}{9}\)
b, \(=-\dfrac{12}{6}+\dfrac{2}{5}=-2+\dfrac{2}{5}=-\dfrac{8}{5}\)
c, \(=\dfrac{27}{13}-1=\dfrac{14}{13}\)
d, \(=\dfrac{12}{11}+\dfrac{7}{19}+\dfrac{12}{19}=\dfrac{12}{11}+1=\dfrac{23}{11}\)
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a) \(\dfrac{2}{9}+\dfrac{-3}{10}+\dfrac{-7}{10}\)
\(=\dfrac{2}{9}+\dfrac{-10}{10}=\dfrac{2}{9}-1=-\dfrac{7}{9}\)
b) \(\dfrac{-11}{6}+\dfrac{2}{5}+\dfrac{-1}{6}\)
\(=-2+\dfrac{2}{5}=-\dfrac{8}{5}\)
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a,\(=\dfrac{2}{9}+\left(\dfrac{-3}{10}+\dfrac{-7}{10}\right)=\dfrac{2}{9}+\left(-1\right)=\dfrac{-7}{9}\)
b,\(=\left(\dfrac{-11}{6}+\dfrac{-1}{6}\right)+\dfrac{2}{5}=-2+\dfrac{2}{5}=\dfrac{-8}{5}\)
c,\(=\dfrac{27}{13}-\left(\dfrac{106}{111}+\dfrac{-5}{111}\right)=\dfrac{27}{13}-1=\dfrac{14}{13}\)
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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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