Question

[Đỗ Minh Anh]

Tính Nhanh:

a)  5/12*4/9+4/9*7/12                                   b) (13/21*7/8-12/21*7/8)*12      c)  7/11+3/4+4/11+8/17+1/4+18/34

Tìm x:

a) 3,71+(632-x)=415

b) 140:(5*x-15)=4

c) 84:(324:18+36-x)+15=19

Answer 1

[Nguyễn Thị Thương Hoài]

a  \(\dfrac{5}{12}\times\dfrac{4}{9}\) + \(\dfrac{4}{9}\times\dfrac{7}{12}\)

= \(\dfrac{4}{9}\times\left(\dfrac{5}{12}+\dfrac{7}{12}\right)\)

= \(\dfrac{4}{9}\times\dfrac{12}{12}\)

= \(\dfrac{4}{9}\)

b(\(\dfrac{13}{21}\times\dfrac{7}{8}-\dfrac{12}{21}\times\dfrac{7}{8}\)) x 12 

(\(\dfrac{7}{8}\times\left(\dfrac{13}{21}-\dfrac{12}{21}\right)\))x 12

\(\dfrac{7}{8}\times\dfrac{1}{21}\) x 12

\(\dfrac{139}{14}\)

Answer 2

[Nguyễn Thị Thương Hoài]

\(\dfrac{7}{11}+\dfrac{3}{4}+\dfrac{4}{11}+\dfrac{8}{17}+\dfrac{1}{4}+\dfrac{18}{34}\)

=\(\left(\dfrac{7}{11}+\dfrac{4}{11}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)\) + \(\dfrac{18}{34}\) 

=1 + 1 + \(\dfrac{18}{34}\)

=\(\dfrac{34}{17}\)