Question

Tính bằng cách thuận tiện nhất:

\(\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{4}{6}+\frac{9}{12}+\frac{16}{20}\)

Answer 1

\(\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{4}{6}+\frac{9}{12}+\frac{16}{20}=\left(\frac{1}{3}+\frac{4}{6}\right)+\left(\frac{1}{4}+\frac{9}{12}\right)+\left(\frac{1}{5}+\frac{16}{20}\right)\)

\(=1+1+1=3\)

Answer 2

Ta có\(\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{4}{6}+\frac{9}{12}+\frac{16}{20}=\left(\frac{1}{3}+\frac{4}{6}\right)+\left(\frac{1}{4}+\frac{9}{12}\right)+\left(\frac{1}{5}+\frac{16}{20}\right)\)

\(=\left(\frac{2+4}{6}\right)+\left(\frac{3+9}{12}\right)+\left(\frac{4+16}{20}\right)\)

\(=\frac{6}{6}+\frac{12}{12}+\frac{20}{20}\)

\(=1+1+1\)

\(=3\)