50*9.813*0.9+13*0.1

问题描述:

50*9.813*0.9+13*0.1

50*9.8
=50*(10-0.2)
=50*10-50*0.2
=500-10
=490
13*0.9+13*0.1
=13*(0.9+0.1)
=13*1
=13