数学简便运算（做得好追加100分）

0.03*(1.34-0.84)
=0.03*0.5
=0.015
1.25*1.7*0.8
=1.7*(1.25*0.8)
=1.7*1
=1.7
8.54-5.98
=8.54-(6-0.02)
=8.54-6+0.02
=2.56
39/（0.5*3.9)
=39/3.9*2
=10*2
=20
53.4/0.25/0.4
上下*2.5
=53.4*10/0.4*2.5
=534
0.75+0.25/0.1
=0.75+2.5
=3.25(这题直接算就行了)
42/3.5
=42*2/(3.5*2)
=42/7*2
=12
(7.2-0.4)*25
=1.8*4*25-0.4*25
=180-10
=170
3.6-36*0.8
=3.6*(1-8)
=-25.2
3.75*0.5+6.25/2
=3.75/2+6.25/2
=(3.75+6.25 )/2
=10/2
=5
6.3*2.1-0.63
=6.3*2.1-6.3*0.1
=6.3*(2.1-0.1)
=6.3*2
=12.6

0.03*(1.34-0.84)
=0.03*0.5
=0.015
1.25*1.7*0.8
=1.25*0.8*1.7
=1*1.7
=1.7

8.54-5.98
=8.54-(6-0.02)
=8.54-6+0.02
=2.54+0.02
=2.56
39/（0.5*3.9)

0.03*0.5=0.015
(1.25*0.8)*1.7=1.7
8.54-6+0.02=2.56
(39/3.9)*(1/0.5)=20
53.4/(0.25*0.4)=534
0.75+2.5=3.25
(42/7)*(1/0.5)=12
0.4*25*(18-1)=170
3.6-3.6*8=3.6*(1-8)=-25.2
3.75*0.5+6.25*0.5=(3.75+6.25)*0.5=5
0.63*21-0.63=0.63*(21-1)=12.6
时间仓促，可能答案不一定准确