Question

[Nguyễn Thị Hà Phương]

(x+5 ) + (x+10 ) + (x+15) + ... +(x+100) = 1110

Answer 1

[Kiệt Nguyễn]

\(\left(x+5\right)+\left(x+10\right)+\left(x+15\right)+...+\left(x+100\right)=1110\)

\(\Leftrightarrow x+5+x+10+x+15+...+x+100=1110\)

\(\Leftrightarrow20x+\left(5+10+15+...+100\right)=1110\)

\(\Leftrightarrow20x+\frac{\left(100+5\right)\left[\left(100-5\right)\div5+1\right]}{2}=1110\)

\(\Leftrightarrow20x+\frac{2100}{2}=1110\)

\(\Leftrightarrow20x+1050=1110\)

\(\Leftrightarrow20x=1110-1050\)

\(\Leftrightarrow20x=60\)

\(\Leftrightarrow x=60\div20\)

\(\Leftrightarrow x=3\)

Vậy x = 3

Answer 2

[Huỳnh Quang Sang]

\((x+5)+(x+10)+(x+15)+...+(x+100)=1110\)

\(\Rightarrow x+5+x+10+x+15+...+x+100=1110\)

\(\Rightarrow(x+x+x+...+x)+(5+10+15+...+100)=1110\)

\(\Rightarrow100x+\frac{(5+100)\cdot20}{2}=1110\)

\(\Rightarrow100x+1050=1110\)

\(\Rightarrow100x=1110-1050\)

\(\Rightarrow100x=60\)

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