Question

用简便方法计算下面各题。0.7×0.4×2.5 8.4×0.25 2.5×6.7×0.8

用简便方法计算下面各题。0.7×0.4×2.5 8.4×0.25 2.5×6.7×0.8 36×10.1 0.68×98 2.8×3.7+1.3×2.8 8.2×9.9 7.24-2.29-3.7 3.2×1.25×25

Answer 1

0.7×0.4×2.5=0.7×（0.4×2.5）=0.7×1=0.7
8.4×0.25=8×0.25+0.4×0.25=2+0.1=2.1
2.5×6.7×0.8=6.7×（2.5×0.8）=6.7×2=13.4
36×10.1=36×10+36×0.1=360+3.6=363.6

0.68×98=0.68×（100-2）=0.68×100-0.68×2=68-1.36=66.64

2.8×3.7+1.3×2.8=2.8×（3.7+1.3）=2.8×5=14
8.2×9.9=8.2×（10-0.1）=8.2×10-8.2×0.1=82-0.82=81.18

7.24-2.29-3.7=（7.24+0.01）-（0.01+2.29）-3.7=7.25-2.3-3.7=7.25-（2.3+3.7）=7.25-6=1.25

3.2×1.25×25=（4×0.8）×1.25×25=4×25×0.8×1.25=100×1=100

Answer 2

0.7*0.4*2.5=0.7*1=0.7
8.4*0.25=2.1*4*0.25=2.1*1=2.1
2.5*6.7*0.8=2.5*4*0.2*6.7=10*0.2*6.72*6.7=13.4
36*10.1=36*（10+0.1）=36+3.6=39.6
0.68*98=0.68*（100-2）=68-1.37=66.63
2.8*3.7+1.3*2.8=2.8*(3.7+1.3)=2.8*5=14
8.2*9.9=8.2*(10-0.1)=82-8.2=73.8
7.24-2.29-3.7=1.25
3.2*1.25*25=(8*1.25)*(0.4*25)=10*10=100

Answer 3

追答

求采纳

Answer 4

追答

求采纳