Question

tính S=\(\dfrac{1}{30}+\dfrac{2}{48}+\dfrac{3}{88}+\dfrac{4}{165}+\dfrac{5}{300}\)

Answer 1

\(S=\dfrac{1}{30}+\dfrac{2}{48}+\dfrac{3}{88}+\dfrac{4}{165}+\dfrac{5}{300}\\ S=\dfrac{1}{5.6}+\dfrac{2}{6.8}+\dfrac{3}{8.11}+\dfrac{4}{11.15}+\dfrac{5}{15.20}\\ S=\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{15}+\dfrac{1}{15}-\dfrac{1}{20}\\ S=\dfrac{1}{5}-\dfrac{1}{20}\\ S=\dfrac{4}{20}-\dfrac{1}{20}\\ S=\dfrac{3}{20}\)