\(\dfrac{14}{17}:\dfrac{17}{32}-\dfrac{14}{17}:\dfrac{17}{15}\\ =\dfrac{14}{17}\times\dfrac{32}{17}-\dfrac{14}{17}\times\dfrac{15}{17}\\ =\dfrac{14}{17}\times\left(\dfrac{32}{17}-\dfrac{15}{17}\right)\\ =\dfrac{14}{17}\times\dfrac{17}{17}\\ =\dfrac{14}{17}\times1\\ =\dfrac{14}{17}\)

\(\Rightarrow\dfrac{14}{17}\times\dfrac{32}{17}-\dfrac{14}{17}\times\dfrac{15}{17}=\dfrac{14}{17}\times\left(\dfrac{32}{17}-\dfrac{15}{17}\right)=\dfrac{14}{17}\times\dfrac{17}{17}=\dfrac{14}{17}\)

a)     12 + 13 + 14 + 15 + 16 + 17+ 18

= (12 + 18) + ( 13 + 17) + (14 + 16) + 15

= 30 + 30 + 30 + 15

=  105

tính bằng cách thuận tiện nhất 6184+309+1516=

A.\(=\frac{17}{25}\times\left(\frac{13}{19}+\frac{6}{19}\right)\)

\(=\frac{17}{25}\times1\)

\(=\frac{17}{25}\)

B\(=\frac{47}{19}:\left(\frac{15}{32}-\frac{15}{17}\right)\)

\(=\frac{47}{19}:1\)

\(=\frac{47}{19}\)

a) 24 + 17 + 26 = (24 + 26) + 17

                         = 50 + 17

                         = 67

b) 80 + 310 + 120 + 90 = (80 + 120) + (310 + 90)

                                    = 200 + 400

                                     = 600

c) 34 + 140 + 60 + 16 = (34  + 16) + (140 + 60)

                                  = 50 + 200

                                  = 250

Câu 2:Đáp số là 8/17 nhé

(5/9+4/9)x8/17

=>1x8/17=8/17

Câu 1: Tìm x:

a)  2/5× x =(thiếu đề)

 8/7: x =4/5 

x=8/7:4/5

x=10/7

Câu 2: Tính bằng cách thuận tiện nhất

5/9× 8/17 + 4/9 × 8/17

=(5/9+4/9)x8/17

=1x8/17=8/17

Số số hạng là 19-11+1=9(số)

Tổng là: 10x9=90

=(11+19)+(12+18)+(13+17)+(14+16)+15

=30+30+30+30+15

=135

90

Câu 1

\(a,\dfrac{2}{5}\times x=4\\ x=4:\dfrac{2}{5}=10\\ b,7:x=\dfrac{4}{5}\\ x=\dfrac{4}{5}\times7=\dfrac{28}{5}\) 

Câu 2

\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)\times\dfrac{8}{17}=1\times\dfrac{8}{17}=\dfrac{8}{17}\)

Câu 1: Tìm x:

a)  2/5× x = 4

x=4 : 2/5

x=10

 8/7: x =4/5 

x=8/7:4/5

x=10/7

Câu 2: Tính bằng cách thuận tiện nhất

5/9× 8/17 + 4/9 × 8/17

=(5/9+4/9)x8/17

=1x8/17=8/17

\(5/9× 8/17 + 4/9 × 8/17 =>(5/9+4/9)×8/17 =>1 ×8/17=8/17\)

A  =\(\frac{2}{5}\times\frac{4}{7}+\frac{3}{5}\times\frac{4}{7}\)  B = \(\frac{17}{13}\times\frac{12}{17}-\frac{4}{13}\times\frac{12}{17}\)   C = \(\frac{9}{14}:\frac{6}{7}+\frac{5}{14}:\frac{6}{7}\)  D =\(\frac{9}{12}:\frac{7}{9}\times\frac{12}{19}\)

=  \(\frac{4}{7}\times\left(\frac{2}{5}+\frac{3}{5}\right)\)              =\(\left(\frac{17}{13}-\frac{4}{13}\right)\times\frac{12}{17}\)                = \((\frac{9}{14}+\frac{5}{14}):\frac{6}{7}\)         = \(\frac{9}{12}\times\frac{9}{7}\times\frac{12}{19}\)

=\(\frac{4}{7}\times1\)                                     = \(1\times\frac{12}{17}\)                                       = \(1:\frac{6}{7}\)                               = \(\frac{9\times9\times12}{12\times7\times19}\)

=\(\frac{4}{7}\)                                              =  \(\frac{12}{17}\)                                                =\(\frac{7}{6}\)                                    = \(\frac{9\times9}{7\times19}=\frac{81}{133}\)

   -  

a) \(\dfrac{16}{15}+\dfrac{7}{15}+\dfrac{4}{15}=\left(\dfrac{16}{15}+\dfrac{4}{15}\right)+\dfrac{7}{15}=\dfrac{20}{15}+\dfrac{7}{15}=\dfrac{27}{15}\)

b) \(\dfrac{5}{17}+\dfrac{7}{17}+\dfrac{13}{17}=\dfrac{5}{17}+\left(\dfrac{7}{17}+\dfrac{13}{17}\right)=\dfrac{5}{17}+\dfrac{20}{17}=\dfrac{25}{17}\)