脱式计算，能用简便方法计算用简便方法．4.5×[7.68÷（8.2-1.8）]4×0.8×12.5×2.54.12-1.78-1.227.8×6.9+2.2×6.9．

Question

脱式计算，能用简便方法计算用简便方法．
4.5×[7.68÷（8.2-1.8）]
4×0.8×12.5×2.5
4.12-1.78-1.22                        
7.8×6.9+2.2×6.9．

Answer 1

（1）4.5×[7.68÷（8.2-1.8）]
=4.5×[7.68÷6.4]
=4.5×1.2
=5.4

（2）4×0.8×12.5×2.5
=（4×2.5）×（0.8×12.5）
=10×10
=100

（3）4.12-1.78-1.22
=4.12-（1.78+1.22）
=4.12-3
=1.12

（4）7.8×6.9+2.2×6.9
=（7.8+2.2）×6.9
=10×6.9
=69