19.5减1.9减2.9减3.9简便方法
问题描述:
19.5减1.9减2.9减3.9简便方法
答
19.5减1.9减2.9减3.9
19.5-(1.9+2.9+3.9)
=19.5-(2+3+4)+0.3
=19.5-9+0.3
=10.8