Question

[Pé ngốc nhí nhảnh]

Tính nhanh

\(\frac{15}{39}\cdot\left(7\frac{4}{5}\cdot1\frac{2}{3}+8\frac{1}{3}\cdot7,8\right)\)

Answer 1

[Phạm Ngọc Sơn]

    \(\frac{15}{39}.\left(7\frac{4}{5}.1\frac{2}{3}+8\frac{1}{3}.7,8\right)\)

\(=\frac{15}{39}.\left(7,8.1\frac{2}{3}+8\frac{1}{3}.7,8\right)\)

\(=\frac{5}{13}.\left\{7,8.\left(1\frac{2}{3}+8\frac{1}{3}\right)\right\}\)

\(=\frac{5}{13}.\left(7,8.10\right)\)

\(=\frac{5}{13}.78\)

\(=30\)