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a)=(3/4+3/12)+2/5
=1+2/15
=17/15
b)
(40/17-6/17)+(47/15-4/30)
=2+3=5
k cho minh
Tinh1 bằng cách thuận tiện nhất :
a ) 3/4 + 2/5 + 3/12
= 3/4 + 2/5 + 1/4
= ( 3/4 + 1/4 ) + 2/5
= 1 + 2/5
= 2/5
b ) 47/15 + 40/17 - 4/30 - 6/17
= 47/15 + 40/17 - 2/15 - 6/17
= ( 47/15 - 2/15 ) + ( 40/17 - 6/17 )
= 45/15 + 34 /17
= 3 + 2
= 5
tk mk nha
thấy thế nào , comment đi
yêu mọi người nhiều lắm !!!
Lời giải:
a. $\frac{3}{4}+\frac{2}{5}+\frac{3}{12}=\frac{3}{4}+\frac{2}{5}+\frac{1}{4}$
$=(\frac{3}{4}+\frac{1}{4})+\frac{2}{5}=1+\frac{2}{5}=\frac{7}{5}$
b. $\frac{47}{15}+\frac{40}{17}-\frac{4}{30}-\frac{6}{17}$
$=(\frac{47}{15}-\frac{4}{30})+(\frac{40}{17}-\frac{6}{17})$
$=(\frac{47}{15}-\frac{2}{15})+\frac{34}{17}$
$=\frac{45}{15}+\frac{34}{17}=3+2=5$
=15/17 x (4/7 + 3/7) - 1/3
=15/17 x 1 - 1/3
=15/17 x (3/3 - 1/3)
=15/17 x 2/3
=30/51
\(\frac{47}{53}\div\frac{17}{52}-\frac{47}{53}\times\frac{35}{17}\)
\(=\frac{47}{53}\times\frac{52}{17}-\frac{47}{53}\times\frac{35}{17}\)
\(=\frac{47}{53}\times(\frac{52}{17}-\frac{35}{17)}\)
\(=\frac{47}{53}\times\frac{17}{17}=\frac{47}{53}\times1=\frac{47}{53}\)
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) \(\dfrac{5}{17}+\dfrac{7}{17}+\dfrac{13}{17}=\dfrac{5}{17}+\left(\dfrac{7}{17}+\dfrac{13}{17}\right)=\dfrac{5}{17}+\dfrac{20}{17}=\dfrac{25}{17}\)
\(\dfrac{14}{17}:\dfrac{17}{32}-\dfrac{14}{17}:\dfrac{17}{15}\\ =\dfrac{14}{17}\times\dfrac{32}{17}-\dfrac{14}{17}\times\dfrac{15}{17}\\ =\dfrac{14}{17}\times\left(\dfrac{32}{17}-\dfrac{15}{17}\right)\\ =\dfrac{14}{17}\times\dfrac{17}{17}\\ =\dfrac{14}{17}\times1\\ =\dfrac{14}{17}\)
= (27/12 + 25/36)+(17/6 + 15/6)= 81/36 + 25/36 + 17/6 + 15/6 = 106/36 + 32/6 = 192/36 + 106/36 = 298/36 = 149/18
= 5
5