9.9+9.98+9.997+9.9996怎样简便计算

问题描述:

9.9+9.98+9.997+9.9996怎样简便计算

原式
=(10-0.1)+(10-0.02)+(10-0.003)+(10-0.0004)
=10+10+10+10-(0.1+0.02+0.003+0.0004)
=40-0.1234
=39.8766

9.9+9.98+9.997+9.9996
=10-0.1+10-0.02+10-0.003+10-0.004
=40-0.1234
=9.8766

9.9+9.98+9.997+9.9996
=10-0.1+10-0.02+10-0.03+10-0.0004
=40-0.1234
=39.8766

=40-(0.1+0.02+0.003+0.0004)
=40-0.1234
=39.8766