Toán Lớp 5: tính tổng sau bằng cách hợp lí nhất: a,24/19+1/15-7/31-5/19 b,(15/16+13/33+1/11)+(7/33-15/16+20/66) c,(21/31-16/7)+(44/53+10/31

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Toán Lớp 5:  tính tổng sau bằng cách hợp lí nhất:    a,24/19+1/15-7/31-5/19  b,(15/16+13/33+1/11)+(7/33-15/16+20/66)     c,(21/31-16/7)+(44/53+10/31)+9/53  d, 2+3/17-5/13-18/35+14/17_17/35-8/13

truongankimtrong · Answer

a) $ frac{24}{19}$+$ frac{1}{15}$-$ frac{7}{31}$-$ frac{5}{19}$=($ frac{24}{19}$-$ frac{5}{19}$)+($ frac{1}{15}$-$ frac{7}{31}$)=1+(-$ frac{74}{465}$)=$ frac{391}{465}$.    b)($ frac{15}{16}$+$ frac{13}{33}$+$ frac{1}{11}$)+($ frac{7}{33}$-$ frac{15}{16}$+$ frac{20}{66}$)=$ frac{15}{16}$+$ frac{13}{33}$+$ frac{1}{11}$+$ frac{7}{33}$-$ frac{15}{16}$+$ frac{20}{66}$=($ frac{15}{16}$-$ frac{15}{16}$)+($ frac{13}{33}$+$ frac{7}{33}$)+($ frac{1}{11}$+$ frac{20}{66}$)=0+($ frac{20}{33}$+$ frac{13}{33}$)=0+1=1    c) ($ frac{21}{31}$-$ frac{16}{7}$)+($ frac{44}{53}$+$ frac{10}{31}$)+$ frac{9}{53}$=$ frac{21}{31}$-$ frac{16}{7}$+$ frac{44}{53}$+$ frac{10}{31}$+$ frac{9}{53}$=($ frac{21}{31}$+$ frac{10}{31}$)-$ frac{16}{7}$+($ frac{44}{53}$+$ frac{9}{53}$)=1-$ frac{16}{7}$+1=-$ frac{2}{7}$.   d) 2+$ frac{3}{17}$-$ frac{5}{13}$-$ frac{18}{35}$+$ frac{14}{17}$-$ frac{17}{35}$-$ frac{8}{13}$=2-($ frac{3}{17}$+$ frac{14}{17}$)-($ frac{5}{13}$+$ frac{8}{13}$)-($ frac{18}{35}$+$ frac{17}{35}$)=2-1-1+1=1.

tuyetnhungthu · Answer

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