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\(\left(y+1\right)+\left(y+4\right)+\left(y+7\right)+....+\left(y+31\right)=231\)
\(\Rightarrow\left(y+y+...+y\right)+\left(1+4+7+...+31\right)=231\)
\(\Rightarrow11y+176=231\)
\(\Rightarrow11y=231-176\)
\(\Rightarrow11y=55\)
\(\Rightarrow y=55:11\)
\(\Rightarrow y=5\)
Vậy y = 5
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a) \(\frac{7}{10}-y\cdot\frac{3}{4}=\frac{1}{5}\)
\(y\cdot\frac{3}{4}=\frac{7}{10}-\frac{1}{5}\)
\(y\cdot\frac{3}{4}=\frac{1}{2}\)
\(y=\frac{1}{2}:\frac{3}{4}\)
\(y=\frac{1}{2}\cdot\frac{4}{3}\)
\(y=\frac{2}{3}\)
b) \(\frac{5}{6}:\left(y+\frac{7}{9}\right)=\frac{3}{4}\)
\(y+\frac{7}{9}=\frac{5}{6}:\frac{3}{4}\)
\(y+\frac{7}{9}=\frac{5}{6}\cdot\frac{4}{3}\)
\(y+\frac{7}{9}=\frac{10}{9}\)
\(y=\frac{10}{9}-\frac{7}{9}\)
\(y=\frac{3}{9}=\frac{1}{3}\)
**** !
a, \(\frac{7}{10}-y\times\frac{3}{4}=\frac{1}{5}\)
\(\Rightarrow y\times\frac{3}{4}=\frac{7}{10}-\frac{1}{5}\)
\(\Rightarrow y\times\frac{3}{4}=\frac{1}{2}\)
\(\Rightarrow y=\frac{1}{2}\div\frac{3}{4}\)
\(\Rightarrow y=\frac{1}{3}\)
b, \(\frac{5}{6}\div\left(y+\frac{7}{9}\right)=\frac{3}{4}\)
\(\Rightarrow y+\frac{7}{9}=\frac{5}{6}\div\frac{3}{4}\)
\(\Rightarrow y+\frac{7}{9}=\frac{10}{9}\)
\(\Rightarrow y=\frac{10}{9}-\frac{7}{9}\)
\(\Rightarrow y=\frac{1}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 7/10 - y × 3/4 = 1/5
y × 3/4 = 7/10 - 1/5
y × 3/4 = 1/2
y = 1/2 : 3/4
y = 2/3. Vậy y = 2/3
b) 5/6 : ( y + 7/9 ) = 3/4
y + 7/9 = 5/6 : 3/4
y + 7/9 = 10/9
y. = 10/9 - 7/9
y = 1/3. Vậy y = 1/3
\(\frac{7}{10}\)- y * \(\frac{3}{4}\)= \(\frac{1}{5}\)
y * \(\frac{3}{4}\)= \(\frac{7}{10}\)- \(\frac{1}{5}\)
y * \(\frac{3}{4}\)= \(\frac{1}{2}\)
y = \(\frac{1}{2}\): \(\frac{3}{4}\)
y = \(\frac{2}{3}\)
Vậy y = \(\frac{2}{3}\)
\(\frac{5}{6}\): ( y + \(\frac{7}{9}\)) = \(\frac{3}{4}\)
y + \(\frac{7}{9}\) = \(\frac{5}{6}\): \(\frac{3}{4}\)
y + \(\frac{7}{9}\) = \(\frac{10}{9}\)
y = \(\frac{10}{9}\)- \(\frac{7}{9}\)
y = \(\frac{3}{9}\)
Vậy y = \(\frac{3}{9}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(y+1)+(y+4)+(y+7)+....+(y+31) = 231
=> (y+y+....+y) + (1+4+7+...+31) = 231
=> 11y + 276 = 231
=> 11y = 55
=> y = 5
Vậy y = 5
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=> (y+y+y+...+y)+(1+4+7+...+28)=155
xet tong 1+4+7+...+28 co: (28-1) /3+1=10 ( so hang) => co 10 so hang y
=> 1+4+7+..+28=(1+28)*10/2=145
=) (y+1)+(y+4)+(y+7)+...+(y+28)=155
=>10y + 145=155
10y=155-145
10y=10
=> y=1
MIH CHAC CHAN DO, duyet DUNG nha
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( 5/7 - y ) * 14/5 = 7/10 + 1/2
( 5/7 - y ) x 14/5 = 6/5
5/7 - y = 6/5 : 14/5
5/7 - y = 3/7
y = 5/7 - 3/7
y = 2/7
![](https://rs.olm.vn/images/avt/0.png?1311)
a)100-9:(372:3.y-1)-14=83
<=>100-9:(124y-1)-14=83
<=>86-9:(124y-1)=83
<=>9:(124y-1)=3
<=>124y-1=3
<=>124y=4
<=>y=\(\frac{1}{31}\approx0,3223\)
b)7260-120:24.y+924=528,3
<=>8184-5y=528,3
<=>5y=7655,7
<=>y=1531,14
c)2000-52:(615:3:y-15)-14=1984
<=>1986-52:(205:y-15)=1984
<=>52:(205:y-15)=2
<=>205:y-15=26
<=>205:y=41
<=>y=5
d)y+y.1/3+5/18=7/18
<=>4/3y=1/9
<=>y=1/12
e)13/15-(5/21+y)7/12=7/10
<=>7/12.(5/21+y)=1/6
<=>5/36+7/12y=1/6
<=>7/12y=1/36
<=>y=1/21\(\approx\)0,4762
h)y+2.y+3.y+...+10.y=49,5
<=>55y=49,5
<=>y=0,9
i)y.(1975/8.9+1885/9.10+1755/10.11+1579/11.12)=1/24
<=>7991,364899y=1/24
<=>y=33/6329161
tích nha mỏi tay quá
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a) Hiệu số phần bằng nhau là : 5 - 2 = 3 ( phần )
Tử số x là : 12 : 3 x 2 = 8
Mẫu số y là : 12 + 8 = 20
Vậy \(\frac{x}{y}=\frac{8}{20}\)
b;c bạn làm tương tự
( y + 1 ) + ( y + 4 ) + ( y + 7 ) + ( y + 10 ) + ... + ( y + 31 ) = 321
( y + y + y + y + ... + y ) + ( 1 + 4 + 7 + 10 + ... + 31 ) = 321
Ta thấy từ 1 đến 31 tạo thành dãy số cách đều 3 đơn vị và từ 1 đến 31 có bao nhiêu số thì tổng ban đầu có bấy nhiêu số y
Từ 1 đến 31 có :
( 31 - 1 ) : 3 + 1 = 11 ( số hạng )
Ta có :
\(y\times11+\frac{\left(31+1\right)\times11}{2}=321\)
y x 11 + 176 = 321
y x 11 = 321 - 176
y x 11 = 145
y = 145 : 11
y = \(\frac{145}{11}\)
Vậy y = \(\frac{145}{11}\)
Học tốt !!! ~
(y+1)+(y+4)+(y+7)+(y+10)+...+(y+31) = 321
y x 11 + (1+4+7+...+10+31) = 321 ( có 11 số y vì ( 31-1) :3 + 1 = 11 ( số))
y x 11 + (1+31) x 11 : 2 = 321
y x 11 + 176 = 321
y x 11 = 145
y = 145/11