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1 # 使用者3013958441215
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2 # 使用者9339127914350
8*(25*15)=(8*25)*15=200*15=3000,
5*4*5*20=(5*4)*(5*20)=20*100=2000,
420/18=420/6/3=70/3,
25*7*4*3=(25*4)*(7*3)=100*21=2100,
15*32*25=(15*8)*(4*25)=120*100=12000。
8x(25x15)
=(4x2)x(25x15)
=(4x25)x(2x15)
=100x30
=3000
2. 5x4x5x20
=5x5x4x20
=25x4x20
=100x20
=2000
3. 420/18
=420/6/3
=70/3
4. 25x7x4x3
=(25x4)x(7x3)
=100x21
=2100
5. 15x32x25
=15x(4x8)x25
=(15x8)x(25x4)
=120x100
=12000