Điền số thích hợp vào chỗ chấm. (1 điểm)

40 m2 80 dm2 = ……………… cm2	9 050 mm2 = ……… cm2 ………. mm2
6 dm2 35 mm2 = ……………… mm2	60 900 cm2 = ……….. m2………. dm2

\(\frac{4}{5}\,\, \times \,\,\frac{6}{7}\,\, + \,\,\frac{4}{5}\,\, \times \,\,\frac{3}{7}\)

\( = \frac{4}{5}\, \times \,\left( {\,\,\frac{6}{7}\,\, + \,\,\frac{3}{7}} \right)\)

\( = \frac{4}{5}\, \times \,\left( {\,\,\frac{{6 + 3}}{{7 \times 5}}\,\,} \right)\)

\( = \frac{4}{5}\, \times \,\frac{9}{7}\)

\( = \frac{{36}}{{35}}\,\)

\(\frac{5}{9}\,\, + \,\,\frac{5}{7}\,\, + \,\,\frac{9}{7}\,\, + \,\,\frac{4}{9}\)

\( = \left( {\frac{5}{9}\,\, + \frac{4}{9}} \right)\, + \,\left( {\frac{5}{7}\,\, + \,\,\frac{9}{7}} \right)\,\,\,\,\)

\( = \frac{9}{9}\, + \,\frac{{14}}{7}\,\,\,\)

= 1 + 2

= 3