23.5+6.5*4.2 9.5*3*2.4 6.4*1.25 怎么简便计算?

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23.5+6.5*4.2 9.5*3*2.4 6.4*1.25 怎么简便计算?

23.5+6.5*4.2 9.5*3*2.4 6.4*1.25 怎么简便计算?
23.5+6.5*4.2 9.5*3*2.4 6.4*1.25 怎么简便计算?

23.5+6.5*4.2 9.5*3*2.4 6.4*1.25 怎么简便计算?
23.5+6.5*4.2
=23.5+6.5+6.5×3.2
=30+6.5×(3+0.2)
=30+19.5+1.3
=49.5+1.3
=50.8
9.5*3*2.4
=(9.5×2)×(3×1.2)
=19×3.6
=(20-1)×3.6
=20×3.6-3.6
=72-3.6
=68.4
6.4*1.25
=0.8×(8×1.25)
=0.8×10
=8