(1+0.3+0.31+0.32……+0.39)×(0.3+0.31+0.32+……+0.39+0.4)-（1+0.3+0.31+0.32……+0.39+0.4）×（0.3+0.31＋0.32+……+0.39）=

(1+0.3+0.31+0.32……+0.39)×[(0.3+0.31+0.32+……+0.39+0.4)-（0.3+0.31＋0.32+……+0.39）]
=(1+0.3+0.31+0.32……+0.39) x 0.1
= (1 + 0.3 x 10 + 0.01 + 0.02...+0.09) x 0.1
= (4 + 0.55 ) x 0.1
= 0.455

设x=1+0.3+0.31+0.32……+0.39。得：
X(X-0.6)-(X+0.4)(X-1)
=X^2-0.6X-(X^2-0.6X-0.4)
=0.4

0.30+0.31+0.32+...+0.39+0.4+0.35=0.7*10/2=3.5
上式=（3.5+1-0.35-0.4）*（3.5-0.35）-（1+3.5-0.35）*（3.5-0.4-0.35）=

(1+0.3+0.31+0.32……+0.39)×(0.3+0.31+0.32+……+0.39+0.4)-（1+0.3+0.31+0.32……+0.39+0.4）×（0.3+0.31＋0.32+……+0.39）
=(1+0.3+0.31+0.32……+0.39)×(0.3+0.31+0.32+……+0.39)+(1+0.3+0.31+0.32……+0.39)×0.4-(1+0.3+0.31+0.32……+0.39)×(0.3+0.31+0.32+……+0.39)-0.4×(0.3+0.31+0.32……+0.39)
=0.4+(0.3+0.31+0.32……+0.39)×0.4-0.4×(0.3+0.31+0.32……+0.39)
=0.4

技巧：巧用乘法分配率.
在式子中+0.4×(0.3+0.31+……+0.39+0.4）,再-0.4×(0.3+0.31+……+0.39+0.4）
原式=（1+0.3+0.31+0.32……+0.39)×(0.3+0.31+0.32+……+0.39+0.4)+0.4×(0.3+0.31+……+0.39+0.4）-（1+0.3+0.31+0.32……+0.39+0.4）×（0.3+0.31＋0.32+……+0.39）-0.4×(0.3+0.31+……+0.39+0.4）
乘法分配率得
原式=（1+0.3+0.31+0.32……+0.39+0.4)×(0.3+0.31+0.32+……+0.39+0.4）-（1+0.3+0.31+0.32……+0.39+0.4）×（0.3+0.31＋0.32+……+0.39）-0.4×(0.3+0.31+……+0.39+0.4）
再次运用乘法分配率得
原式=（1+0.3+0.31+0.32……+0.39+0.4)×0.4-0.4×(0.3+0.31+……+0.39+0.4）
再次运用乘法分配率得
原式=1×0.4
=0.4

希望对你解题有所帮助