Tính: \(\Large{A=10\times(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfr

Tính:

\(\Large{A=10\times(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20})}\)

• A. Đáp án: 8

\(\Large{A=10\times(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20})}\)

= \(\Large{A=10\times(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5})}\)

= \(\Large{A=10\times(\dfrac{1}{1} - \dfrac{1}{5})}\)

= \(\Large{A=10\times\dfrac{4}{5}}\)

= 8

Đáp số: 8