1. 0.9+9.9+99.9+999.9+9999.9
=10.8+99.9+999.9+9999.9
=1110.6+9999.9
=11110.5
2. 8.8×1.25
=（8+0.8）×1.25
=8×1.25+0.8×1.25
=10+1
11
3. 0.125×32×25
=0.125×（4×8）×25
=（0.125×8）×（4×25）
=1×100
=100
4. 9999×2222+3333×3334
=3333×6666+3333×3334
=3333×（6666+3334）
=33330000
5. 20072007×2008-20082008×2007
=2007×10001×2008-2008×10001×2007
=0
6. 123.123×234-234.234×123
=123×1.001×234-234×1.001×123
=0
7. 3.89×4.4+0.611×44
=3.89×4.4+6.11×4.4
=（3.89+6.11）×4.4
=10×4.4
=44
8. 0.111×3.7+0.777×0.9
=0.111×3.7+0.111×6.3
=0.111×（3.7+6.3）
=0.111×10
=1.11
3+5+7=15
12+19+8=39
23+19+27=69
27+14+3=44
29+18+11=58
36+16+4=56
38+19+12=69
42+19+18=79
