Question

[Phạm Lê Khánh Chi]

Tính bằng cách thuận tiện

a) \(\frac{5}{11}x\frac{7}{25}+\frac{15}{11}x\frac{1}{5}\)

b) \(\frac{3}{7}x\frac{25}{19}-\frac{1}{7}x\frac{18}{19}\)

Answer 1

[Kiyotaka Ayanokoji]

a, \(\frac{5}{11}\times\frac{7}{25}+\frac{15}{11}\times\frac{1}{5}\)

\(=\frac{5}{11}\times\frac{7}{25}+\frac{5}{11}\times\frac{3}{5}\)

\(=\frac{5}{11}\times\left(\frac{7}{25}+\frac{3}{5}\right)\)

\(=\frac{5}{11}\times\frac{22}{25}\)

\(=\frac{2}{5}\)

b, \(\frac{3}{7}\times\frac{25}{19}-\frac{1}{7}\times\frac{18}{19}\)

\(=\frac{1}{7}\times\frac{75}{19}-\frac{1}{7}\times\frac{18}{19}\)

\(=\frac{1}{7}\times\left(\frac{75}{19}-\frac{18}{19}\right)\)

\(=\frac{1}{7}\times3\)

\(=\frac{3}{7}\)