递等式能巧算的要巧算 120*4*0.25*0.7 5.1*75-49*7.5-1 (20+9.744/2.4)*0.5-1.93

120*4*0.25*0.7
=120×1×0.7
=12×7
=84

5.1*75-49*7.5-1
=75×(5.1-4.9)-1
=75×0.2-1
=15-1
=14

(20+9.744/2.4)*0.5-1.93
=(20+4.06)×1/2-1.93
=10+2.03-1.93
=10+0.1
=10.1

120*4*0.25*0.7
=120*0.7*4*0.25
=84*1
=84
5.1*75-49*7.5-1
=5.1*75-4.9*75-1
=75*（5.1-4.9）-1
=75*0.2-1
=15-1
=14
(20+9.744/2.4)*0.5-1.93
=(20+4.06)*0.5-1.93
=20*0.5+4.06*0.5-1.93
=10+2.03-1.93
=10+0.1
=10.1