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x : 637 = 2345
=>x= 2345 x 637
=> x =1493765
4000 - x =138
=> x =4000 - 138
=> x = 3862
212552 : x = 326
=>x = 212552 : 326
=> x =652
( x + 1233 ) - 1978 = 9876
=>(x+1233) = 11854
=> x =10621
x : 2 : 3 = 138
=>x:2 = 138 . 3 = 414
=> x = 828
x + 223 = 876 - 326
x + 223 = 550
x = 550 - 223
x = 327
Vậy x = 327
a) \(\dfrac{5}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{5}{7}\)
\(=\dfrac{5}{7}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)
\(=\dfrac{5}{7}\times1\)
\(=\dfrac{5}{7}\)
b) \(\dfrac{1}{10}+\dfrac{5}{9}+\dfrac{4}{9}+\dfrac{9}{10}-1\)
\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\left(\dfrac{1}{10}+\dfrac{9}{10}-1\right)\)
\(=1+0\)
\(=1\)
c) \(\dfrac{5}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{5}{7}+\dfrac{2}{7}\)
\(=\dfrac{5}{7}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\dfrac{2}{7}\)
\(=\dfrac{5}{7}+\dfrac{2}{7}\)
\(=1\)
d) \(\dfrac{2}{7}+\dfrac{2}{8}+\dfrac{1}{4}+\dfrac{1}{7}+\dfrac{4}{7}\)
\(=\left(\dfrac{2}{8}+\dfrac{1}{4}\right)+\left(\dfrac{2}{7}+\dfrac{1}{7}+\dfrac{4}{7}\right)\)
\(=\left(\dfrac{1}{4}+\dfrac{1}{4}\right)+1\)
\(=\dfrac{1}{2}+1\)
\(=\dfrac{3}{2}\)
e) \(\dfrac{4}{5}+\dfrac{3}{10}+\dfrac{2}{10}+0,7\)
\(=\dfrac{4}{5}+\dfrac{5}{10}+\dfrac{7}{10}\)
\(=\dfrac{4}{5}+\dfrac{12}{10}\)
\(=\dfrac{4}{5}+\dfrac{6}{5}\)
\(=\dfrac{10}{5}\)
\(=2\)
g) \(362\times728+326\times272\)
\(=326\times\left(728+272\right)\)
\(=326\times1000\)
\(=326000\)
326 x 728 + 327 x 272
= 326 x 728 + 326 x 272 + 272
= 326 x ( 728 +272 ) + 272
= 326 x 1000 + 272
= 326000 + 272
= 326272
326 x 728 + 327 x 272
= 326 x 728 + 326 x 272 + 272
= 326 x (728 + 272) + 272
= 326 x 1000 + 272
= 326000 + 272
= 326272
x - 45,5 + 326 = 453
x - 45,5 = 453 - 326 = 127
x = 127 + 45,5
x = 172,5
328 x 17 x (1859 - 326) x (49 x 24 - 98 x 12)
= 328 x 17 x 1533 x 0
= 0
Tính nhanh:
328 x 17 x ( 1859 - 326 ) x ( 49 x 24 - 98 x 12 )
= 328 x 17 x 1533 x 0
=0
:D
212 552 : x = 326
x = 212552 : 326
x = 652
\(212552:x=326\\ x=212552:326\\ x=652\)