3.计算下列各题,能简算的要简算。
12.25+4.2+7.75+5.8 19.4×0.9+0.1×19.4
5.6-0.71-0.29 7.2×0.3+0.3×0.8
0.4×3.14×2.5 9.4×[3.6÷(5.4÷0.9)]

12.25+4.2+7.75+5.8
=(12.25+7.75)+(4.2+5.8)
=20+10
=30
19.4×0.9+0.1×19.4
=19.4×(0.9+0.1)
=19.4×1
=19.4
5.6-0.71-0.29
=5.6-(0.71+0.29)
=5.6-1
=4.6
7.2×0.3+0.3×0.8
=0.3×(7.2+0.8)
=0.3×8
=2.4
0.4×3.14×2.5
=0.4×2.5×3.14
=1×3.14
=3.14
9.4×[3.6÷(5.4÷0.9)]
=9.4×[3.6÷6]
=9.4×0.6
=5.64