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a) 67+135+33=(67+33)+135=100+135=235
b) 277+13+323+87=(277+323)+(113+87)=600+200=800
c) 29+132 + 237 + 868 + 763=29+(132+868)+(237+763)=29+1000+1000=2029
d) 652 + 327 + 148 + 15 + 73=(652+148)+(327+73)+15=800+400+15=1215
e) 463 + 318 + 137 + 22=(463+137)+(318+22)=600+340=940
g) 189 + 424 +511 + 276 + 55=(189+511)+(424+276)+55=700+700+55=1455
h) (321 +27) + 79=(321+79)+27=400+27=427
i) 185+434+515+266+155=(185+515)+(434+266)+155=700+700+155=1555
k) 168 + 79 + 132=(168+132)+79=300+79=379
l) 29 + 132 + 237 + 868 + 763=29+(132+868)+(237+763)=29+1000+1000=2029
S = 1/3+1/9+1/27+1/81+1/243+1/729+1/2187 ( 1 )
Nhân S với 3. Ta có:
S x 3 = 1 + 1/3 + 1/9 + 1/27 + 1/81 + 1/243 + 1/729 ( 2 )
Trừ ( 2 ) với ( 1 ) ta có:
S x 3 - S = 1 - 1/ 2187
2S = 2186/ 2187
S = 2186/ 2187 : 2
S = 1093/ 2187
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. 9999.997 + 9999 + 9999 + 9999
= 9999.(997 + 1 + 1 + 1)
= 9999 . 1000
= 9999000
b. (456 . 11 + 912) . 37 : 13 : 74
= (5016 + 912) . 37 : 13 : 74
= 219336 : 13 : 74
= 16872 : 74
= 228
c. 864 . 48 - 432 . 96 : 864 . 48 . 432
= (864 . 48 - 432 . 96) : (864 . 48 . 432)
= 0 : (864 . 48 . 432)
= 0
a. 9999.997 + 9999 + 9999 + 9999
= 9999.(997 + 1 + 1 + 1)
= 9999 . 1000
= 9999000
b. (456 . 11 + 912) . 37 : 13 : 74
= (5016 + 912) . 37 : 13 : 74
= 219336 : 13 : 74
= 16872 : 74
= 228
c. 864 . 48 - 432 . 96 : 864 . 48 . 432
= (864 . 48 - 432 . 96) : (864 . 48 . 432)
= 0 : (864 . 48 . 432)
= 0
a) \(=23\left(64+37-1\right)=23.100=2300\)
ý b bn ghi rõ lại đầu bài đc ko ạ
a) ko ghi lại đề
\(=23.\left(64+37\right)-23\)
\(=2300-23\)
\(=2277\)