1200-31/40=47969/40

câu 2 =45/56+25/56=(45+25)/56=70/56=5/4

19.9+9.(37+43)+9

=19.9+9.80+9

=9.(19+80+1)

=9.100

=900

\(19\times9+9\times\left(37+43\right)+9\)

\(=19\times9+9\times80+9\times1\)

\(=9\times\left(80+19+1\right)\)

\(=9\times100\)

\(=900\)

     \(19\times9+9\times\left(37+43\right)+9\)

\(=9\left[19+\left(37+43\right)+1\right]\)

\(=9\left[\left(19+1\right)+\left(37+43\right)\right]\)

\(=9\times100\)

\(=900\)

=\(\frac{36.950+36.726+36.324}{\left(29+1\right).15:2-152}\)

=\(\frac{36.\left(950+726+324\right)}{73}\)

=\(\frac{36.2000}{73}\)

=\(\frac{72000}{73}\)

\(\frac{36\times950+18\times726\times2+3\times324\times12}{1+3+5+7+9+....+27+29+31-152}\)

\(=\frac{36\times950+\left(18\times2\right)\times726+324\times\left(12\times3\right)}{\left(31+1\right)\times16\div2-152}\)

\(=\frac{36\times950+36\times726+324\times36}{256-152}\)

\(=\frac{36\times\left(950+726+324\right)}{104}\)

\(=\frac{36\times2000}{104}=\frac{72000}{104}=\frac{9000}{13}\)

a) = \(\left(\dfrac{2}{7}+\dfrac{4}{7}+\dfrac{1}{7}\right):\dfrac{27}{31}\)

= \(\dfrac{7}{7}\) x \(\dfrac{31}{27}\)

= 1 x \(\dfrac{31}{27}\) = \(\dfrac{31}{27}\)

b) = \(\left(\dfrac{23}{45}:\dfrac{23}{45}\right)\)x \(\dfrac{17}{51}\)

= 1 x \(\dfrac{17}{51}\)= \(\dfrac{17}{51}\)

mnvhjvjhviviuih

2,9x(98.7 - 68,7 - 28, 7 )

=2,9 x 1,3

=3,77

  98,7 x 2,9 - 68,7 x 2,9 - 28,7 x 29

= 98,7 x 2,9 - 68,7 x 2,9 - 287 x 2,9 

= 2,9 x ( 98,7 - 68,7 - 287 )

= -745,3 

(4,329 : 0,001 - 43,2 x 100) x 150 + 2018 + 2019 : 10000

= (4,329 x 1000 - 4320) x 150 + 2018 + 2019 : 10000

= (4329 - 4320) x 150 + 2018 + 2019 : 10000

= 9 x 150 + 2018 + 0,2019

= 1350 + 2018 + 0,2019

= 3368 + 0,2019

= 3368,2019

Muốn tính nhanh phép này thì phần trong ngoặc phải thay 43,2 thành 43,29 nhé bạn.

a) 3 2/7 - 2/5 + 5/7 - 3/5

= 3 + 2/7 - (2/5 + 3/5) + 5/7

= 3 + (2/7 + 5/7) - 1

= 3 + 1 - 1

= 3

b) 5 4/7 - 4/9 + 1 3/7 - 5/9

= 5 + 4/7 - 4/9 + 1 + 3/7 - 5/9

= (5 + 1) + (4/7 + 3/7) - (4/9 + 5/9)

= 6 + 1 - 1

= 6

a) \(3\dfrac{2}{7}-\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{3}{5}\)

\(=\left(\dfrac{23}{7}+\dfrac{5}{7}\right)-\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)

\(=4-1\)

\(=3\)

b) \(5\dfrac{4}{7}-\dfrac{4}{9}+1\dfrac{3}{7}-\dfrac{5}{9}\)

\(=\left(\dfrac{32}{7}+\dfrac{10}{7}\right)-\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)

\(=6-1\)

\(=5\)

a) \(3\dfrac{2}{7}-\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{3}{5}\)

\(=\left(\dfrac{23}{7}+\dfrac{5}{7}\right)-\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)

\(=4-1\)

\(=3\)

b) \(5\dfrac{4}{7}-\dfrac{4}{9}+1\dfrac{3}{7}-\dfrac{5}{9}\)

\(=\left(\dfrac{39}{7}+\dfrac{10}{7}\right)-\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)

\(=7-1\)

\(=6\)