19.9+19.98+19.997+19.996 巧算

问题描述:

19.9+19.98+19.997+19.996 巧算

19.9+19.98+19.997+19.996
=20-0.1+20-0.02+20-0.003+20-0.004
=80-(0.1+0.02+0.003+0.004)
=80-0.127
=79.873