Question

Tìm x nếu : (x+1)+(x+6)+(x+11)+...+(x+96)=990

Answer 1

Câu hỏi của Nguễn Thị Thu Trang - Toán lớp 5 - Học toán với OnlineMath

Answer 2

Bài làm:

Ta có: \(\left(x+1\right)+\left(x+6\right)+\left(x+11\right)+...+\left(x+96\right)=990\)

\(\Leftrightarrow\left(x+x+...+x\right)+\left(1+6+11+...+96\right)=990\)

\(\Leftrightarrow20\times x+\frac{\left(96+1\right)\times20}{2}=990\)

\(\Leftrightarrow20\times x+970=990\)

\(\Leftrightarrow20\times x=20\)

\(\Leftrightarrow x=1\)

Vậy x = 1

Học tốt!!!!

Answer 3

\(\left(x+1\right)+\left(x+6\right)+\left(x+11\right)+...+\left(x+96\right)=990\)

<=> \(\left(x+x+x+...+x\right)+\left(1+6+11+...+96\right)=990\)

<=> \(20x+\frac{\left(96+1\right)\cdot\left[\left(96-1\right)\div5+1\right]}{2}=990\)

<=> \(20x+970=990\)

<=> \(20x=20\)

<=> \(x=1\)

Answer 4

\(\left(x+1\right)+\left(x+6\right)+\left(x+11\right)+...+\left(x+96\right)=990\)

\(\Leftrightarrow\left(x+x+x+...+x\right)+\left(1+6+11+...+96\right)=990\)

\(\Leftrightarrow20x+\frac{\left(96+1\right).\left[\left(96-1\right):5+1\right]}{2}=990\)

\(\Leftrightarrow20x+970=990\)

\(\Leftrightarrow20x=20\)

\(\Leftrightarrow x=1\)

Vậy \(x=1\)