Tính nhanh
a ) 2 /3 x 8 / 17 + 2 /3 x 5 / 17 + 2/ 3 x 4 / 17
b) 35,16 - 44,84 : 4 + 15,6 x 24
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a, 35,16-44,84:4+15,6.24
=35,16-11.21+374,4
=398,35
b, Thay a=20,11 vào 2,75.a+7,25.a. Ta có:
2,75.20,11+7,25.20,11
=20,11.(2,75+7,25)
=20,11.10
=201,11
a,35,16-44,84:4+15,6x24
=35,16-11,21+373,4
=23,95+373,4
=397,35
b, 45,651x73+45,651x20+45,651x7
=45,651x(73+20+7)
=45,651x100
=4565,1
c, 305,765x100+305,765x0,001
=305,765x(100+0,001)
=305,765x100,001
=30576,80577
1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)
\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)
=0
2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)
\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)
\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)
3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)
\(=\dfrac{52546}{15}\)
4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
=10,5.4,8-2,4
=50,4-2,4
=48
=35,16-11,21+374,4
=23,95+374,4
=398,35
a)2/3x(8/17+5/17+4/17)=2/3x1=2/3
b)35,16-44,84:4+15,6x24=35,16-11,21+374,4=398,35
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