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a,Cách 1: (6/11 + 5/11 ) x 3/7 Cách 2 :(6/11 + 5/11) x 3/7
= 1 x 3/7 =6/11 x 3/7 + 5/11 x 3/7
= 3/7 = 18/77 + 15/77
= 3/7
b, Cách 1:3/5 x 7/9 - 3/5 x 2/9 Cách 2 :3/5 x 7/9 - 3/5 x 2/9
= 7/15 - 2/15 = 3/5 x (7/9 - 2/9 )
= 1/3 = 3/5 x 5/9
= 1/3
c, Cách 1:(6/7 - 4/7) : 2/5 Cách 2: ( 6/7- 4/7 ) : 2/5
= 2/7 : 2/5 = 6/7 : 2/5 - 4/7 : 2/5
= 5/7 = 15/7 - 10/7
= 5/7
d,Cách 1:8/15 : 2/11 + 7/15 : 2/11 Cách 2:8/15 : 2/11 +7/15 : 2/11
= 88/30 + 77/30 =(8/15+7/15) :2/11
= 11/2 = 1 : 2/11
= 11/2
Bài 2 cậu tự làm nhé !
a, \(\frac{2}{3}:\frac{5}{7}:\frac{x}{9}=\frac{2}{7}:\frac{3}{5}:\frac{10}{9}\Leftrightarrow\frac{2\times7\times9}{3\times5\times x}=\frac{2\times5\times9}{7\times3\times10}\Leftrightarrow\frac{42}{5\times x}=\frac{3}{7}\Leftrightarrow294=15\times x\Leftrightarrow x=19,6\)
Các phần sau tương tự.
Dùng phương pháp nhân chéo và kiểm tra trình độ tính toán, khả năng rút gọn.
Thay kết quả vào x để kiểm tra lại bài.
Bài 1:
a) \(x.\dfrac{3}{4}=\dfrac{9}{14}\)
\(\Rightarrow x=\dfrac{9}{14}:\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{6}{7}\)
b) \(x:\dfrac{5}{9}=\dfrac{3}{10}\)
\(\Rightarrow x=\dfrac{3}{10}.\dfrac{5}{9}\)
\(\Rightarrow x=\dfrac{1}{6}\)
`a, 3/4 + 1/2 xx 7/2`
`= 3/4 + 7/4`
`=10/4`
`=5/2`
`b, 6/15 - 1/3 : 5/3`
`= 6/15 - 1/3 xx 3/5`
`= 6/15 - 3/15`
`= 3/15`
`=1/5`
`c, x-4/9 = 3/7 : 9/4`
`=> x-4/9= 3/7 xx 4/9`
`=> x-4/9= 12/63`
`=> x-4/9=4/21`
`=> x= 4/21 +4/9`
`=>x= 40/63`
`d, 7/9 xx 3/5 -1/2=1/5`
`->` sao lại bằng có `x` ko vậy ạ?
`a,`
`3/4+1/2 \times 7/2=3/4+7/4=10/4=5/2`
`b,`
`6/15 - 1/3 \div 5/3=6/15-1/5=1/5`
`c,` Tìm x?
`x-4/9=3/7 \div 9/4`
`x-4/9=4/21`
`x=4/21+4/9`
`x=40/63`
`d, 7/9x \times 3/5-1/2=1/5`
`7/9x \times 3/5=1/5+1/2`
`7/9x \times 3/5=7/10`
`7/9x=7/10 \div 3/5`
`7/9x=7/6`
`x=7/6 \div 7/9=3/2`
2 : \(buổi \) \(sáng\) \(bán\) \(dc :\)
\((360 - 142 : 2 =109 l\)
\(buổi\) \(chiều\) \(bán\) \(dc :\)
\(360 - 109 = 251 l\)
\(1,\)
\(a,x\times\dfrac{3}{9}=\dfrac{9}{15}\) \(b,x:\dfrac{1}{2}=\dfrac{5}{6}\)
\(x=\dfrac{9}{15}:\dfrac{3}{9}\) \(x=\dfrac{6}{5}\times\dfrac{1}{2}\)
\(x=\dfrac{81}{45}=\dfrac{9}{5}\) \(x=\dfrac{6}{10}=\dfrac{3}{5}\)
\(2,\) có bạn làm rồi nhé ;>
\(3,\)
\(a,\dfrac{7}{12}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{7}{12}+\left(\dfrac{3}{4}\times\dfrac{2}{9}\right)=\dfrac{7}{12}+\dfrac{1}{6}=\dfrac{7}{12}+\dfrac{2}{12}=\dfrac{7+2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)
\(b,\dfrac{8}{9}-\dfrac{4}{15}:\dfrac{2}{5}=\dfrac{8}{9}-\left(\dfrac{4}{15}:\dfrac{2}{5}\right)=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{8-6}{9}=\dfrac{2}{9}\)
a) x - 3/2 = 4/3
x = 4/3 + 3/2
x = 8/6 + 9/6 = 17/6
b) 2/5 * x = 1/3
x = 1/3 : 2/5
x = 1/3 x 5/2 = 5/6
c) x - 4/9 = 3/7 : 9/14
x - 4/9 = 2/3
x = 2/3 + 4/9
x = 6/9 + 4/9 = 10/9
d) 3/5 * x - 1/2 = 1/5
3/5 * x = 1/5 + 1/2 = 7/10
x = 7/10 : 3/5
x = 7/10 * 5/3 = 7/6
a/\(x-\dfrac{3}{2}=\dfrac{4}{3}\)
\(x=\dfrac{4}{3}+\dfrac{3}{2}\)
\(x=\dfrac{17}{6}\)
b/\(\dfrac{2}{5}\times x=\dfrac{1}{3}\)
\(x=\dfrac{1}{3}:\dfrac{2}{5}\)
\(x=\dfrac{5}{6}\)
c/\(x-\dfrac{4}{9}=\dfrac{3}{7}:\dfrac{9}{14}\)
\(x-\dfrac{4}{9}=\dfrac{2}{3}\)
\(x=\dfrac{2}{3}+\dfrac{4}{9}\)
\(x=\dfrac{10}{9}\)
d/\(\dfrac{3}{5}\times x-\dfrac{1}{2}=\dfrac{1}{5}\)
\(\dfrac{3}{5}\times x=\dfrac{1}{5}+\dfrac{1}{2}\)
\(\dfrac{3}{5}\times x=\dfrac{7}{10}\)
\(x=\dfrac{7}{10}:\dfrac{3}{5}\)
\(x=\dfrac{7}{6}\)
a, (6/11+5/11)x3/17
c1:=1x3/17
=3/17
c2:=6/11x3/17+5/11x3/17
=18/197+15/187
=33/187
=3/17
b,3/5x7/9-3/5x2/9
c1:=21/45-6/45
=15/45
=1/3
c2:=3/5x(7/9-2/9)
=3/5x5/9
=1/3
c,( 6/7-4/7):2/5
c1:=2/7:2/5
=2/7x5/2
=5/7
c2,6/7:2/5-4/7:2/5
=6/7x5/2-4/7x5/2
=15/7-10/7
=5/7
d,8/15:2/11+7/15:2/11
c1:=(8/15+7/15):2/11
=1x11/2
=11/2
c2:=8/15x11/2+7/15x11/2
=88/30+77/30
=165/30
=11/2
a) (\(\frac{6}{11}\) + \(\frac{5}{11}\)) x \(\frac{3}{17}\)= \(\frac{11}{11}\) x \(\frac{3}{17}\)= \(1\) x\(\frac{3}{17}\)= \(\frac{3}{17}\)
b) \(\frac{3}{5}\)x\(\frac{7}{9}\)- \(\frac{3}{5}\)x \(\frac{2}{9}\) = \(\frac{3}{5}\)x (\(\frac{7}{9}\)- \(\frac{2}{9}\))= \(\frac{3}{5}\) x \(\frac{5}{9}\)= \(\frac{3}{9}\)
c) (\(\frac{6}{7}\)- \(\frac{4}{7}\)) : \(\frac{2}{5}\)= \(\frac{2}{7}\) x \(\frac{5}{2}\)= \(\frac{5}{7}\)
d) \(\frac{8}{15}\) : \(\frac{2}{11}\) + \(\frac{7}{15}\): \(\frac{2}{11}\)= ( \(\frac{8}{15}\)+ \(\frac{7}{15}\)) x \(\frac{11}{2}\)= 1 x \(\frac{11}{2}\)= \(\frac{11}{2}\)
Chúc học tốt nha!
\(a)\frac{3}{5}+\frac{2}{15}\)
\(=\frac{9}{15}+\frac{2}{15}\)
\(=\frac{11}{15}\)
\(b)4-\frac{2}{3}\)
\(=\frac{12-2}{3}\)
\(=\frac{10}{3}\)
\(=3\frac{1}{3}\)
\(c)X\times\frac{3}{4}=\frac{4}{9}:3\)
\(X\times\frac{3}{4}=\frac{4}{27}\)
\(X=\frac{4}{27}:\frac{3}{4}\)
\(X=\frac{8}{81}\)
\(2\times X=\frac{3}{5}\)
\(X=\frac{3}{5}:2\)
\(X=\frac{3}{10}\)
\(X:\frac{5}{7}=2\)
\(X=2\times\frac{5}{7}\)
\(X=\frac{10}{7}\)