1. (2018五上·古冶期中) 脱式计算，能简算的要简算。

①0.25×7.5×4.

②0.63×99

③79.2×108-8×79.2

④1.23×9.4+0.77×9.4

⑤（2.1+6.9÷0.15）÷0.1

⑥3.27×99+3.27

⑦21÷3.5+21÷1.5