Tính bằng cách thuận tiện a) 524 × 63 + 524 × 37 – 2 400 b) 7/9 x 6/5 + 6/5 x 2/9 + 4/5

a) 524 × 63 + 524 × 37 – 2 400

= 524 × (63 + 37) – 2 400

= 524 × 100 – 2 400

= 52 400 – 2 400

= 50 000

b) \(\frac{7}{9}\, \times \,\,\frac{6}{5}\,\, + \,\,\frac{6}{5}\, \times \,\,\frac{2}{9}\,\, + \,\,\frac{4}{5}\)

 \(\begin{array}{l} = \left( {\frac{7}{9} + \frac{2}{9}} \right) \times \frac{6}{5} + \frac{4}{5}\\ = \frac{6}{5} + \frac{4}{5}\\ = \frac{{10}}{5}\\ = 2\end{array}\)