Question

[Choi Yuna]

A=\(\frac{16}{20.24}+\frac{16}{24.28}+\frac{16}{28.32}+....+\frac{16}{76.80}\)

Answer 1

[Đặng Viết Thái]

\(A=4\left(\frac{1}{20}-\frac{1}{80}\right)=4.\frac{3}{80}=60\)

Answer 2

[Huỳnh Quang Sang]

\(A=\frac{16}{20\cdot24}+\frac{16}{24\cdot28}+\frac{16}{28\cdot32}+...+\frac{16}{76\cdot80}\)

\(A=4\left[\frac{4}{20\cdot24}+\frac{4}{24\cdot28}+\frac{4}{28\cdot32}+...+\frac{4}{76\cdot80}\right]\)

\(A=4\left[\frac{1}{20}-\frac{1}{24}+...+\frac{1}{76}-\frac{1}{80}\right]\)

\(A=4\left[\frac{1}{20}-\frac{1}{80}\right]\)

\(A=4\left[\frac{4}{80}-\frac{1}{80}\right]=4\cdot\frac{3}{80}=\frac{4\cdot3}{80}=\frac{1\cdot3}{20}=\frac{3}{20}\)