19.8+29.7+39.6+49.5简算

问题描述:

19.8+29.7+39.6+49.5简算

20-0.2+30-0.3+40-0.4+50-0.5
=20+30+40+50-(0.2+0.3+0.4+0.5)
=140-1.4
=138.6