1. $0.125×67×8$ $1.85×4×2.5$
$125×32×0.25$ $1.25×2.5×8×4$
答案：1. 0.125×67×8
=0.125×8×67
=1×67
=67
【点拨】运用了乘法交换律简算。
1.85×4×2.5
=1.85×（4×2.5）
=1.85×10
=18.5
【点拨】运用了乘法结合律简算。
125×32×0.25
=125×（8×4）×0.25
=（125×8）×（4×0.25）
=1000×1
=1000
【点拨】运用了乘法结合律简算。
1.25×2.5×8×4
=（1.25×8）×（2.5×4）
=10×10
=100
【点拨】运用了乘法交换律与乘法结合律简算。
2. $5.6×9.9+5.6×0.1$ $5.17+5.17×99$
$6.3×9.8$ $10.1×45$
$6.54×17.8-6.54×7.8$ $3.6×5.9+3.6×4.1$
$41.7×4.3+43×0.71+512×0.43$
$2.75×47+27.5×2.8+27.5×2.5$
答案：2. 5.6×9.9+5.6×0.1
=5.6×（9.9+0.1）
=5.6×10
=56
5.17+5.17×99
=5.17×（1+99）
=5.17×100
=517
6.3×9.8
=6.3×（10-0.2）
=6.3×10-6.3×0.2
=63-1.26
=61.74
10.1×45
=（10+0.1）×45
=10×45+0.1×45
=450+4.5
=454.5
6.54×17.8-6.54×7.8
=6.54×（17.8-7.8）
=6.54×10
=65.4
3.6×5.9+3.6×4.1
=3.6×（5.9+4.1）
=3.6×10
=36
41.7×4.3+43×0.71+512×0.43
=41.7×4.3+4.3×7.1+51.2×4.3
=（41.7+7.1+51.2）×4.3
=100×4.3
=430
2.75×47+27.5×2.8+27.5×2.5
=27.5×4.7+27.5×2.8+27.5×2.5
=27.5×（4.7+2.8+2.5）
=27.5×10
=275
3. $19.23÷0.25÷0.4$ $7.8÷1.25÷0.8$
$6.9÷(2.3×5)$ $5.4÷(0.9×0.2)$
答案：3. 19.23÷0.25÷0.4
=19.23÷（0.25×0.4）
=19.23÷0.1
=192.3
7.8÷1.25÷0.8
=7.8÷（1.25×0.8）
=7.8÷1
=7.8
6.9÷（2.3×5）
=6.9÷2.3÷5
=3÷5
=0.6
5.4÷（0.9×0.2）
=5.4÷0.9÷0.2
=6÷0.2
=30
4. $1.28+7.4+8.72$ $12.37+4.69+5.31$
答案：4. 1.28+7.4+8.72
=1.28+8.72+7.4
=10+7.4
=17.4
【点拨】运用了加法交换律简算。
12.37+4.69+5.31
=12.37+（4.69+5.31）
=12.37+10
=22.37
【点拨】运用了加法结合律简算。
5. $8.75-0.96-0.04$ $15.76-(5.76-3.28)$
$82.5-30.17-7.83$ $24.8-12.73-(4.8+6.27)$
$12.58-6.4+1.42-3.6$ $15.25-4.72-5.28+4.75$
答案：5. 8.75-0.96-0.04
=8.75-（0.96+0.04）
=8.75-1
=7.75
15.76-（5.76-3.28）
=15.76-5.76+3.28
=10+3.28
=13.28
82.5-30.17-7.83
=82.5-（30.17+7.83）
=82.5-38
=44.5
24.8-12.73-（4.8+6.27）
=24.8-12.73-4.8-6.27
=（24.8-4.8）-（12.73+6.27）
=20-19
=1
12.58-6.4+1.42-3.6
=（12.58+1.42）-（6.4+3.6）
=14-10
=4
15.25-4.72-5.28+4.75
=（15.25+4.75）-（4.72+5.28）
=20-10
=10
