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1 - 2/7 = 7/7 - 2/7 = 5/7
15/42 - 2/7 = 15/42 - 12/47 = 3/47
6/5 x 3 = 18/5
7/3 x 2/5 = 14/15
`1-2/7=7/7-1/7=6/7`
`15/42-2/7=15/42-12/42=3/42=1/14`
`6/5xx3=(6xx3)/5=18/5`
`7/3xx2/5=(7xx2)/(3xx5)=14/15`
B1:
\(13956-8768=5188\)
\(4368:78=56\)
\(4512:96=47\)
\(1665:45=37\)
3:
\(A=2\left(\dfrac{2}{5\cdot7}+\dfrac{2}{7\cdot9}+...+\dfrac{2}{53\cdot55}\right)\)
=2(1/5-1/7+1/7-1/9+...+1/53-1/55)
=2(1/5-1/55)
=2*10/55
=2*2/11
=4/11
b, 3/5 + 4/7 + 2/8 + 10/25 + 9/21 + 28/16
= 3/5 + 4/7 + 2/8 + 2/5 + 3/7 + 14/8
= (3/5 + 2/5) + ( 4/7 + 3/7) + ( 2/8 + 14/8)
= 1 + 1 + 7/4
= 2 + 7/4 = 15/4
c , 8/7 + 7/6 + 5/8 + 10/12 + 24/28 + 6/16
= c , 8/7 + 7/6 + 5/8 + 5/6 + 6/7 + 1/2
= (8/7 + 6/7) + (7/6 + 5/6) + 5/8 + 1/2
= 14/7 + 12/6 + 5/8 + 1/2
= 2 + 2 + 5/8 + 1/2
= 4 + 9/8 = 41/8
Tìm x:
\(a.\dfrac{35}{28}-x=\dfrac{5}{14}\\ x=\dfrac{35}{28}-\dfrac{5}{14}\\ x=\dfrac{25}{28}\\ b.\dfrac{6}{7}\times x=\dfrac{2}{3}\\ x=\dfrac{2}{3}:\dfrac{6}{7}\\ x=\dfrac{7}{9}\\ c.x\times7=\dfrac{3}{4}\\ x=\dfrac{3}{4}:7\\ x=\dfrac{3}{28}\\ d.2:x-\dfrac{1}{3}=\dfrac{2}{5}\\ 2:x=\dfrac{2}{5}+\dfrac{1}{3}\\ 2:x=\dfrac{11}{15}\\ x=2:\dfrac{11}{15}\\ x=\dfrac{30}{11}.\)
\(a,\dfrac{35}{28}-x=\dfrac{5}{14}\)
\(x=\dfrac{35}{28}-\dfrac{5}{14}\)
\(x=\dfrac{25}{28}\)
\(b,\dfrac{6}{7}\times x=\dfrac{2}{3}\)
\(x=\dfrac{2}{3}:\dfrac{6}{7}\)
\(x=\dfrac{7}{9}\)
\(c,x\times7=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}:7\)
\(x=\dfrac{3}{28}\)
\(d,2:x-\dfrac{1}{3}=\dfrac{2}{5}\)
\(2:x=\dfrac{2}{5}+\dfrac{1}{3}\)
\(2:x=\dfrac{11}{15}\)
\(x=2:\dfrac{11}{15}\)
\(x=\dfrac{30}{11}\)
#YVA
\(\frac{5}{7}+\frac{3}{4}=\frac{41}{28}\)\(Đ\)
\(3+\frac{2}{5}=1\)\(S\)
\(\frac{11}{9}-\frac{5}{6}=\frac{7}{18}\)\(Đ\)
\(4-\frac{3}{7}=\frac{25}{7}\)\(Đ\)
\(x+\frac{4}{11}=\frac{3}{5}\).
\(x=\frac{3}{5}-\frac{4}{11}\)
\(x=\frac{13}{55}\)
Vậy ta chọn câu C
dung hay sai
5/7 + 3/4 = 41/28 .....Đ...
3 + 2/5 = 1....S....
11/9 - 5/6 = 7/18....Đ...
4 - 3/7 = 25/7.....
tim x
x + 4/11 =3/5
Đáp án : C .13/55
\(\frac{3}{4}.\frac{5}{7}=\frac{3.5}{4.7}=\frac{15}{28}\)
\(\frac{15}{28}:\frac{5}{7}=\frac{15.7}{28.5}=\frac{105}{140}=\frac{21}{28}\)
\(\frac{1}{7}.\frac{1}{5}=\frac{1}{7.5}=\frac{1}{35}\)
\(\frac{3}{4}x\frac{5}{7}=\frac{15}{28}\)
\(\frac{15}{28}:\frac{5}{7}=\frac{15}{28}x\frac{7}{5}=\frac{105}{140}=\frac{3}{4}\)
\(\frac{1}{7}x\frac{1}{5}=\frac{1}{35}\)
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