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(a+1)+(a+2)+(a+3)+(a+4)+(a+5) = 65
a x 5 + ( 1 + 2 + 3+ 4 +5) = 65
a x 5 + 15 =65
a x 5 = 65 -15
ax 5 = 50
a = 50 :5
a = 10
(a + 1) + (a + 2) + (a + 3) + (a + 4) + (a + 5) = 65
= a x 5 + 1 + 2 + 3 + 4 + 5 = 65
= a x 5 = 65 - 1 - 2 - 3 - 4 - 5 = 50
Vay a = 50 : 5 = 10
x la chu x ke chu z
![](https://rs.olm.vn/images/avt/0.png?1311)
=> (a + a+a+a+a ) + (1+2+3+4+5) =65
=>5a + 15 = 65
=> 5a =65-15 = 40
=>a = 40 :5 = 8
Vậy a = 8 nhaOnline Math
(a + 1) + (a + 2) + (a+ 3) + (a + 4)+(a + 5) = 65
= a x 5 + (1 + 2 + 3 + 4 + 5) = 65
= a x 5 + 15 = 65
= a x 5 = 50
=> a = 50 : 5 = 10
Đáp số; 10
![](https://rs.olm.vn/images/avt/0.png?1311)
Đặt \(A=\) \(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{a\left(a+1\right)}=\frac{49}{100}\)
\(\Rightarrow A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{a}-\frac{1}{a+1}=\frac{49}{100}\)
\(\Rightarrow A=\frac{1}{2}-\frac{1}{a+1}=\frac{49}{100}\)
\(\)\(\Rightarrow\frac{1}{a+1}=\frac{1}{2}-\frac{49}{100}\)
\(\)\(\Rightarrow\frac{1}{a+1}=\frac{1}{100}\Rightarrow a+1=100\Rightarrow a=100-1\)
\(\Rightarrow a=99\)
Vậy \(a=99\)k cho mik nha :))
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a: \(1-\left(5\dfrac{4}{9}+a-7\dfrac{7}{18}\right):15\dfrac{3}{4}=0\)
=>\(\left(5+\dfrac{4}{9}+a-7-\dfrac{7}{18}\right):\dfrac{63}{4}=1\)
=>\(\left(a-2+\dfrac{1}{18}\right)=\dfrac{63}{4}\)
=>\(a-\dfrac{35}{18}=\dfrac{63}{4}\)
=>\(a=\dfrac{63}{4}+\dfrac{35}{18}=\dfrac{637}{36}\)
b: \(B=\left(\dfrac{2}{15}+\dfrac{5}{3}-\dfrac{3}{5}\right):\left(4\dfrac{2}{3}-2\dfrac{1}{2}\right)\)
\(=\dfrac{2+5\cdot5-3^2}{15}:\left(4+\dfrac{2}{3}-2-\dfrac{1}{2}\right)\)
\(=\dfrac{2+4^2}{15}:\left(2+\dfrac{2}{3}-\dfrac{1}{2}\right)\)
\(=\dfrac{18}{15}:\dfrac{13}{6}=\dfrac{6}{5}\cdot\dfrac{6}{13}=\dfrac{36}{65}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
(a.5)+(1+2+3+4+5)=65
(a.5)+15=65
a.5=65-15
a.5=50
a=50:5
a=10 tíck mình nhé
(a + 1 ) + (a +2 ) + (a + 3 ) + (a + 4 ) + ( a + 5 ) = 65
a+1+a+2+a+3+a+4+a+5 = 65
(a+a+a+a+a)+(1+2+3+4+5)= 65
(ax5)+15 = 65
ax5= 50
a=10
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có 5 x a + (1+2+3+4+5) = 65
5 x a = 65 - 15
5 x a = 50 Vậy a = 50 : 5 nên a = 10 . Giải theo toán Tiểu học
![](https://rs.olm.vn/images/avt/0.png?1311)
=> ( a + a + a + a + a ) + ( 1 +2 + 3 + 4 + 5 ) = 65
=> 5a + { [ 5 . ( 5 + 1 ) ] : 2 } = 65
=> 5a + 15 = 65
=> 5a = 65 - 15
=> 5a = 50
=> a = 50 : 5
=> a = 10
![](https://rs.olm.vn/images/avt/0.png?1311)
a) Ta có:
1; 4; 7;...; 100 có (100 - 1) : 3 + 1 = 34 (số)
1 + 4 + 7+ ... + 100 = (100 + 1) × 34 : 2
= 101 × 17
(1 + 4 + 7 + ... + 100) : a = 17
101 × 17 : a = 17
a = 101 × 17 : 17
a = 100
b) (X - 1/2) × 5/3 = 7/4 - 1/2
(X - 1/2) × 5/3 = 5/4
X - 1/2 = 5/4 : 5/3
X - 1/2 = 3/4
X = 3/4 + 1/2
X = 5/4
a) (1 + 4 + 7 +...+ 100) : a = 17
1717 : a = 17
a = 101
b) \(\left(x-\dfrac{1}{2}\right)\times\dfrac{5}{3}=\dfrac{7}{4}-\dfrac{1}{2}\)
\(\left(x-\dfrac{1}{2}\right)\times\dfrac{5}{3}=\dfrac{10}{8}\)
\(\left(x-\dfrac{1}{2}\right)=\dfrac{10}{8}\div\dfrac{5}{3}\)
\(\left(x-\dfrac{1}{2}\right)=\dfrac{10}{8}\times\dfrac{3}{5}\)
\(\left(x-\dfrac{1}{2}\right)=\dfrac{3}{4}\)
\(x-\dfrac{1}{2}=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}+\dfrac{1}{2}\)
\(x=\dfrac{5}{4}\)
(a + 1) + (a + 2) + (a + 3) + (a + 4) + (a + 5) = 115
Suy ra a + 1 + a + 2 + a + 3 + a + 4 + a + 5 = 115
Suy ra 5a + ( 1 + 2 + 3 + 4 + 5 ) = 115
Suy ra 5a + 15 = 115
Suy ra 5a = 115 - 15
Suy ra 5a = 100
Suy ra a = 100/5
Suy ra a = 20
Vậy số cần tìm là 20
(a + 1) + (a + 2) + (a + 3) + (a + 4) + (a + 5) = 115
<=> a + 1 + a + 2 + a + 3 + a + 4 + a + 5 = 115
<=> 5a + (1 + 2 + 3 + 4 + 5) = 115
<=> 5a + 15 = 115
<=> 5a = 115 - 15
<=> 5a = 100 <=> a = 20
Vậy a = 20