\(A=\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{152.155}\)
\(A=\frac{1}{3}.\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{152}-\frac{1}{155}\right)\)
\(A=\frac{1}{3}.\left(\frac{1}{2}-\frac{1}{155}\right)\)
\(A=\frac{1}{3}.\frac{153}{310}\)
\(A=\frac{51}{310}\)
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