1. 简便运算(要写步骤)
11.
0.25*39+10.1*3.7=0.25*(40-1)+(10+0.1)*3.7=0.25*40-0.25*1+3.7*10+3.7*0.1=10-0.25+3.7*10+0.37
=10*(1+3.7)+0.37-0.25=47.12
12.
3.6*100.1-2.34*9.9=3.6*(100+0.1)-2.34*(10-0.1)=360+0.36-23.4+0.234=336.6+0.594=337.194
13.
14.02-3.5+0.98-6.5=14.02+0.98-(6.5+3.5)=15-10=5
14.
999.8+99.8+9.8+0.2*3=999.8+0.2+99.8+0.2+9.8+0.2
=1000+100+10=1110
15.
180/125+7/2.5=180/125+7*50/(2.5*50)=(180+350)/125=530/125=106/25
16.
457*9.9+45.7=457*9.9+457*0.1=457*(9.9+0.1)=457*10=4570
17.
0.456*101-45.6=0.456*101-0.456*100=0.456*(101-100)=0.456
18.
1.248*125*0.4*20=1.248*(125*0.4)*20=1.248*50*20=1.248*1000=1248
19.
1.5+1.5/3-6*0.2=1.5+0.5-1.2=0.8
20.
(1.5+1.5)/3+6/0.2=1+30=31
12题我怀疑题目有点问题,你没把运算符号搞错吧
2. 数学简便运算(要写步骤)
66.86-8.66-1.34 =66.86-(8.66+1.34)=66.86-10=56.8617.8/(1.78*4) =17.8/1.78/4=10/4=2.53.65*10.1=3.65*(10+0.1)=3.65*10+3.65*0.1=36.5+0.365=36.86515.2/0.25/4 =15.2/(0.25*4)=15.2/1=15.27.2*0.2+2.4*1.4 =2.4*3*0.2+2.4*1.4=2.4*0.6+2.4*1.4=2.4*(0.6+1.4)=2.4*2=4.818-1.8/0.125/0.8 =18-1.8/(0.125*0.8)=18-1.8/0.1=18-18=00.79*199 =0.79*(200-1)=0.79*200-0.79*1=158-0.79=157.213.9/(1.3*5) =3.9/1.3/5=3/5=0.60.35*1.25*2*0.8 =(0.35*2)*(1.25*0.8)=0.7*1=0.715/0.25=15/(0.5*0.5)=15/0.5/0.5=30/0.5=60。