Luyện tập

`( 13/12 + 4/3) : 2/3`

`= ( 13/12 + 16/12 ) : 2/3`

`= 29/12 : 2/3`

`= 29/12 xx 3/2`

`=29/8`

__ 

`( 5/6 - 3/8) x 2 1/2`

`=(40/48 - 18/48) xx 5/2`

`=11/24 xx 5/2`

`=55/48`

`3/5+4/7`

`=21/35+20/35`

`=41/35`

\(\dfrac{3}{5}+\dfrac{4}{7}=\dfrac{21}{35}+\dfrac{20}{35}=\dfrac{41}{35}\)

\(\dfrac{3}{5}+\dfrac{4}{7}\left(MC:35\right)\\ =\dfrac{3\times7}{5\times7}+\dfrac{4\times5}{7\times5}\\ =\dfrac{21}{35}+\dfrac{20}{35}\\ =\dfrac{41}{35}.\)

B)

`10/3:5/6=10/3xx6/5=4`

`=>C

C)

`12:6/5+4/7`

`=12xx5/6+4/7`

`=10+4/7`

`=70/7+4/7`

`=74/7`

`=>B`

`2/3xx4=(2xx4)/3=8/3`

`=>B`

`3 : 6/5`

`= 3 xx 5/6`

`= 15/6`

__

`4 : 6/7`

`= 4 xx 7/6`

`= 28/6`

`= 14/3`

__

`x xx 11/8=33/20`

`=> x= 33/20 : 11/8`

`=> x= 33/20 xx 8/11`

`=>x=6/5`

__

`5 : x =4/7`

`=> x= 5 : 4/7`

`=> x= 5 xx 7/4`

`=> x= 35/4`

Bài 1.

\(\left(\dfrac{2}{3}-\dfrac{1}{4}\right)\times\dfrac{1}{2}=\dfrac{5}{12}\times\dfrac{1}{2}=\dfrac{5}{24}\)

\(\left(\dfrac{2}{3}-\dfrac{1}{4}\right)\times\dfrac{1}{2}=\dfrac{2}{3}\times\dfrac{1}{2}-\dfrac{1}{4}\times\dfrac{1}{2}=\dfrac{1}{3}-\dfrac{1}{8}=\dfrac{8}{24}-\dfrac{3}{24}=\dfrac{5}{24}\)

Bài 2.

\(\dfrac{47}{16}:\dfrac{5}{2}=\dfrac{47}{16}\times\dfrac{2}{5}=\dfrac{94}{80}=\dfrac{47}{40}\)

\(\dfrac{5}{8}:\dfrac{4}{15}=\dfrac{5}{8}\times\dfrac{15}{4}=\dfrac{75}{32}\)

`(2/3-1/4) xx 1/2`

`= (8/12 -3/12) xx 1/2`

`= 5/12 xx 1/2`

`= 5/24`

__

`(2/3-1/4) xx 1/2`

`= 2/3 xx 1/2 - 1/4 xx 1/2`

`= 2/6 - 1/8`

`= 1/3 -1/8`

`=5/24`

`47/16 : 5/2`

`= 47/16 xx 2/5`

`=47/40`

__

`5/8 : 4/15`

`= 5/8 xx 15/4`

`= 75/32`

\(1.\)

\(\left(\dfrac{2}{3}-\dfrac{1}{4}\right)\times\dfrac{1}{2}=\left(\dfrac{8}{12}-\dfrac{3}{12}\right)\times\dfrac{1}{2}=\dfrac{5}{12}\times\dfrac{1}{2}=\dfrac{5}{24}\)

\(\left(\dfrac{2}{3}-\dfrac{1}{4}\right)\times\dfrac{1}{2}=\left(\dfrac{2}{3}\times\dfrac{1}{2}\right)-\left(\dfrac{1}{4}\times\dfrac{1}{2}\right)=\dfrac{1}{3}-\dfrac{1}{8}=\dfrac{8}{24}-\dfrac{3}{24}=\dfrac{5}{24}\)

\(2.\)

\(\dfrac{47}{16}:\dfrac{5}{2}=\dfrac{47}{16}\times\dfrac{2}{5}=\dfrac{94}{80}=\dfrac{47}{40}\)

\(\dfrac{5}{8}:\dfrac{4}{15}=\dfrac{5}{8}\times\dfrac{15}{4}=\dfrac{75}{32}\)

Bài 1: 

`5/8 - 3/8 = 2/8 = 1/4`

`23/8- 7/8 = 16/8 = 2`

`17/24 - 1/3 = 17/24 - 8/24 = 9/24 = 3/8`

Bài 2: 

`5/7 + 10/13 xx 5/7 + 15/13 xx 5/7 + 1/13 xx 5/7`

`= 5/7 xx (1 + 10/13 + 15/13 + 1/13)`

`= 5/7 xx (1 + 26/13)`

`= 5/7 xx (1 + 2)`

`= 5/7 xx 3`

`= 15/7`

`5/8-3/8=(5-3)/8= 2/8=1/4`

`23/8 - 7/8=(23-7)/8=16/8=2`

`17/24 - 1/3=17/24 -  8/24=(17-8)/24= 9/24= 3/8`

`5/7 + 10/13 xx 5/7 + 15/13 xx 5/7 + 1/13 xx 5/7`

`= 5/7 xx ( 10/13 + 15/13 + 1/13+1 )`

`=5/7 xx3`

`=15/7`

\(y\times\dfrac{2}{3}=\dfrac{1}{4}+\dfrac{1}{1}\)

\(y\times\dfrac{2}{3}=\dfrac{1}{4}+\dfrac{4}{4}\)

\(y\times\dfrac{2}{3}=\dfrac{5}{4}\)

\(y=\dfrac{5}{4}:\dfrac{2}{3}\)

\(y=\dfrac{5}{4}\times\dfrac{3}{2}\)

\(y=\dfrac{15}{8}\)

anh/chị nào giúp em với :33  😗 

2/5 tấn = 400 kg     6m2 115m2 = 1210000cm2       8124m = 8 km 124 m
1/5 km = 200 m      3/5 phút = 36 giây             40m2 8dm2 = 4008 dm2
điền dấu : a.7/9 .<.. 7/8    b.4/28 .=.. 1/7      c.8/6 ..>. 5/8       d.15/15 .=.. 4/4
khoang tròn vào câu trl đúng : 2 đường chéocủa hình thoi có độ dài lần lượt là 12dm và 8dm. Diện tích của hình thoi là:    a.96dm2    b.40dm2     c.192dm2     d.128dm2                                 ở đây có sai j k ạ vì DT hình thoi=tích 2 đường   chéo:2=12x8=96:2=48 chứ nhỉ
biết y là số lẻ chia hết cho 5 và 438 < y < 449 : a.439    b.440   c.448    d.445