1.135+3.3465.557+7.768+9.979怎么解答?

1.135+3.346+5.557+7.768+9.979
=1.135+9.979+3.346+7.768+5.557
=11.114+11.114+5.557
=5.557*5
=27.785那9.8+99.8+999.8+9999.8+99999.8和1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19和2.89X4.68+4.68X6.11+4.68怎么解答？（用简便方法）9.8+99.8+999.8+9999.8+99999.8=(10-0.2)+(100-0.2)+(1000-0.2)+(10000-0.2)+(100000-0.2)=(10+100+1000+10000+100000)-5*0.2=111110-1=1111091.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19=(1.1+9.9) +(3.3+7.7)+5.5+(11.11+19.19)+(13.13+17.17)+15.15这题与第一题类似2.89X4.68+4.68X6.11+4.68=4.68*(2.89+6.11+1)=4.68*10=46.8 提公因式那17.48X37-17.48X19+17.48X82怎么用简便方法解答？跟前面一题一样啊提公因式17.48X37-17.48X19+17.48X82=17.48*（37-19+82）=17.48*100=1748