Question

[Hoàng Khánh Ly]

1. Tính nhanh:

A, \(\dfrac{7}{9}\) x \(\dfrac{25}{28}\) x \(\dfrac{9}{7}\) 

B, \(\dfrac{4}{7}\) x \(\dfrac{17}{18}\) x \(\dfrac{7}{4}\) x \(\dfrac{18}{17}\) 

Giúp mình với ạ. Mình sẽ tick

Answer 1

[Sahara]

a/\(\left(\dfrac{7}{9}\times\dfrac{9}{7}\right)\times\dfrac{25}{28}\)
\(=1\times\dfrac{25}{28}\)
\(=\dfrac{25}{28}\)
b/\(\dfrac{4}{7}\times\dfrac{17}{18}\times\dfrac{7}{4}\times\dfrac{18}{17}\)
\(=\left(\dfrac{4}{7}\times\dfrac{7}{4}\right)\times\left(\dfrac{17}{18}\times\dfrac{18}{17}\right)\)
\(=1\times1\)
\(=1\)