Question

Answer 1

\(B=11\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\right)\)

\(=11\cdot\left(\dfrac{1}{2}-\dfrac{1}{10}\right)=11\cdot\dfrac{4}{10}=\dfrac{44}{10}=\dfrac{22}{5}\)

Answer 2

\(B=11\left(\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\right)\)

\(B=11\left(\dfrac{1}{4}+\dfrac{1}{12}+\dfrac{1}{24}+\dfrac{1}{40}\right)\)

\(B=11.\dfrac{2}{5}=\dfrac{22}{5}\)