Tính nhanh:
a/ 4/6+7/13+17/9-8/9+19/13+14/6 b/ 328/435x468/432x435/164x432/984x164/468
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a) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}-\dfrac{8}{9}+\dfrac{14}{6}+\dfrac{19}{13}\)
\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}-\dfrac{8}{9}+\dfrac{7}{3}+\dfrac{19}{13}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}-\dfrac{8}{9}\right)\)
\(=\dfrac{9}{3}+\dfrac{26}{13}+\dfrac{9}{9}\)
\(=3+2+1\)
\(=6\)
b) \(\dfrac{328}{435}\times\dfrac{468}{432}\times\dfrac{435}{164}\times\dfrac{432}{984}\times\dfrac{164}{468}\)
\(=\dfrac{328\times468\times435\times432\times164}{435\times432\times164\times984\times468}\)
\(=\dfrac{328}{984}\)
\(=\dfrac{1}{3}\)
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
a) \(\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{10}{16}+\dfrac{10}{24}\)
\(=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}\)
\(=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\)
\(=1+1\)
\(=2\)
b) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{14}{6}\)
\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{7}{3}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)
\(=3+2+2\)
\(=7\)
c) \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)
\(=1-\dfrac{1}{7}\)
\(=\dfrac{6}{7}\)
a: =y x15/5=3y
b: =(4/6+14/6)+(7/13+19/13)+(17/9-8/9)
=3+2+1
=6
Một mảnh đất HCN có chiều dài 90cm chiều rộng bằng 3/5 chiều dài. Tính chu vi mảnh vườn đó
4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6
= ( 4/6 + 14/6 ) + ( 7/13 + 19/13 ) + ( 17/9 + 1/9 )
= 18/6 + 26/13 + 18/9
= 3 + 2 + 2 = 7
a)
= (4/6+14/6)+(7/13+19/13)-(17/9-8/9)
= 3 + 2 - 1
= 4 ( Thể : 5-1 Xuống dòng = 4)