数学计算题 能简便要简便 速度

1、(5/6)-(0.15+(9/20))/1.8
=(5/6)-(0.15+0.45)/1.8
=(5/6)-(0.6)/1.8
=(5/6)-2/6
= 0.5
2、((2/39)+(10/27))*27/(1/39)
=((2/39)+(10/27))*27*39)
=2*27+10*39
= 444
3、(2/25)*(3/8)+(1/16)*(3/25)
= 6/200+3/400
=15/400
= 0.0375
4、((13/15)+(8/17))*(3/4)+(3/4)*((2/15)+(9/17))
=(3/4)((13/15)+(8/17)+(2/15)+(9/17))
=(3/4)((13/15)+(2/15)+(8/17)+(9/17))
=(3/4)(1+1)
=(3/4)*2
= 1.5