72与73的相乘有没有速算方法？

72×73=72×（70+3）
=72×70+3×（70+2）
=（72+3）×70+3×2
=75×70+6
=(70+5)×70+6
=70×70+350+6
=4900+350+6
=5256

用去尾法速算法:
(72+3)*(73-3)+2*3=75*70+6=5250+6=5256
用补整法法速算法:
方法2:(72+8)*(73-8)+(80-72)*(80-73)
=65*80+8*7
=5200+56
=5256

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