Question

[khanhngan]

B= 1/30 + 1/42 + 1/56 + 1/72 + 1/90 + 1/110 + 1/132

Answer 1

[Nông Hữu Thái Dương]

\(\frac{1}{5x6}+\frac{1}{6x7}+\frac{1}{7x8}+\frac{1}{8x9}+\frac{1}{9x10}+\frac{1}{10x11}+\frac{1}{11x12}\)

\(=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{11}-\frac{1}{12}\)

  =1/5-1/12=7/60

Answer 2

[Cao Ngọc Kiều Nhi]

B= 1/30 + 1/42 + 1/56 + 1/72 + 1/90 + 1/110 + 1/132= 7/60