下列递等式如何巧算

解：
346.7÷40÷2.5
=346.7÷(40×2.5)
=346.7÷100
=3.467

24.44×2.5
=(20+4+0.4+0.04)×2.5
=20×2.5+4×2.5+0.4×2.5+0.04×2.5
=50+10+1+0.1
=61.1

17.6+2.4÷2.5×4
=17.6+（2.5-0.1）×4÷2.5
=17.6+4(1-1/25)
=17.6+4-4*0.04
=21.44

7.7×10.01
=7.7×(10+0.01 )
=77+0.077
=77.077

(4.8-0.8×3.7)÷1.6
=4.8÷1.6-0.8×3.7÷1.6
=3-3.7÷2
=3-1.85
=1.15

38.2×0.98
=38.2×(1-0.02)
=38.2×1-38.2×0.02
=38.2-0.764
=37.436

29×0.29-2.9+29×0.81
=29×0.29-29×0.1+29×0.81
=29×(0.29-0.1+0.81)
=29×1
=29

38.2×0.98
=38.2×(1-0.02)
=38.2×1-38.2×0.02
=38.2-0.764
=37.436

17.6-1.1×8.3
=1+8.3×2-1.1×8.3
=8.3×(2-1.1)+1
=8.3×0.9+1
=8.47

4.31×0.99
=4.31×1-4.31×0.01
=4.31-0.0431
=4.2669

2.5都能够化成10
346.7/(40*2.5)=3.467
24.44*2.5=6.11*4*2.5=61.1
什么0.99 0.98看成1-0.01，1-0.02就好

反正思路就是这样