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\(\frac{3}{10}\div\frac{5}{9}+\frac{4}{15}\div\frac{1}{5}\)
\(=\frac{27}{50}+\frac{4}{3}\)
\(=\frac{281}{150}\)
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y + y x 1/3 : 2/9 + y : 2/7 = 360
=> y + y x 1/3 x 9/2 + y x 7/2 = 360
=> y + y x 3/2 + y x 7/2 = 360
=> y x ( 1 + 3/2 + 7/2 ) = 360
=> y x 6 = 360
=> y = 360 : 6
=> y = 60
Vậy y = 60
Chúc bạn học tốt !!!
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\(\frac{1}{2}+\frac{1}{3}\cdot\frac{1}{5}:\frac{2}{3}\)
\(=\frac{1}{2}+\frac{1}{3}\cdot\frac{3}{10}\)
\(=\frac{1}{2}+\frac{1}{10}\)
\(=\frac{3}{5}\)
chúc bạn học tốt nhé ^..^
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Đặt A=1+1/3+1/6+1/10+ ... + 1/45
1/2.A=1/2+1/6+1/12+1/20+ ... + 1/90
1/2.A= 1/1.2+1/2.3+1/3.4+1/4.5+ ... + 1/9.10
1/2A= 1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+ ... +1/9-1/10
1/2.A= 1-1/10
1/2.A=9/10
A=(9/10).2
A=9/5
Sai thì thôi đấy
bài này lớp 4 mà mình không làm được nhỉ . mình học dốt dốt quá .
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\(S=\frac{3}{5.7}+\frac{3}{7.9}+.....+\frac{3}{59.61}\)
\(=\frac{3}{2}.\left(\frac{2}{5.7}+\frac{2}{7.9}+......+\frac{2}{59.61}\right)\)
=\(\frac{3}{2}.\left(\frac{7-5}{5.7}+\frac{9-7}{7.9}+......+\frac{61-59}{59.61}\right)\)
=\(\frac{3}{2}.\left(\frac{7}{5.7}-\frac{5}{5.7}+\frac{9}{7.9}-\frac{7}{7.9}+.....+\frac{61}{59.61}-\frac{59}{59.61}\right)\)
=\(\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+.....+\frac{1}{59}-\frac{1}{61}\right)\)
=\(\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{61}\right)\)
=\(\frac{3}{2}.\frac{56}{305}\)
=\(\frac{84}{305}\)
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a, 3/22 x 3/11 x 22
Cách 1
3/22 x 3/11 x 22 = 9/242 x 22
= 198/242
= 9/11
Cách 2
3/22 x 3/11 x 22 = 3 x 3 x 22/22 x 11 x 1
= 9/11
b,( 1/2 + 1/3) x 2/5
Cách 1
( 1/2 + 1/3 ) x 2/5 = 5/6 x 2/5
= 10/30
= 1/3
Cách 2
( 1/2 +1/3) x 2/5 = 1/2 x 2/5 + 1/3 x 2/5
= 2/10 + 2/15
= 1/5 + 2/15
= 3/15 + 2/15
= 5/15
= 1/3
c, 3/5 x 17/21 + 17/21 x 2/5
Cách 1
3/5 x 17/21 + 17/21 x 2/5 = 51/105 + 34/105
= 85/105
= 17/21
Cách 2
3/5 x 17/21 + 17/21 x 2/5 = 17/21 x (3/5 +2/5)
= 17/21 x 5/5
= 17/21 x 1
= 17/21
HỌC TỐT ( k mk nhé)
`1/2+1/3+5/9`
`=9/18+6/18+10/18`
`=25/18`
1/2 + 1/3 + 5/9
\(=\dfrac{27}{54}+\dfrac{28}{54}\) + \(\)\(\dfrac{30}{54}\)
= 85/54
HT