2/5×4+1/5×2/13+2/5×12/13用简便运算

问题描述:

2/5×4+1/5×2/13+2/5×12/13用简便运算

2/5×4+1/5×2/13+2/5×12/13
=8/5+2/5×(1+12)/13
=8/5+2/5
=2