递等式计算，能巧算的要巧算。

①4.78+0.4+1.6

②10.38- 3.3 – 6.7

③5.02-2.8+1.98

④93.45- 8.6 - 3.45

⑤41+8.68+49+1.32

⑥3.9+0.1-3.9+0.1