Question

1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19怎样简便计算的答案

Answer 1

1+3+5+7+9+11+13+15+17+19 等差数列
=10*(1+19)/2=100

1+3+5+7+9=5*(1+9)/2=25 等差数列

1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19
=1+3+5+..+19+(1+3+5+7+9+1.1+1.3+1.5+1.7+1.9)/100
=100+(25+5+25/10)/100
=100+(32.5)/10=103.25

Answer 2

1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19
=1+0.1+3+0.3+5+0.5+7+0.7+9+0.9+11+0.11+13+0.13+15+0.15+17+0.17+19+0.19
=(1+3+5+……+19)+(0.1+0.3+0.5+0.7+0.9)+(0.11+0.13+0.15+0.17+0.19)
=(1+19)*10/2+2.5+0.75
=100+2.5+0.75
=103.25

Answer 3

解：原式=1.1×（1＋3＋5＋7＋9）＋1.01×（11＋13＋15＋17＋19）
=1.1×25＋1.01×75
=27.5＋75.75
=103.5
（注：任何数乘以11，结果是：两边一拉中间相加。ab×101＝abab,abc×1001＝abcabc）

Answer 4

(1+3+5+7+9+11+13+15+17+19)×1.1