$解：何亮的成績更穩(wěn)定，理由如下：$
$ \because \overline{x}_{趙明}=\frac {1}{5}\times (25+23+27+29+21)=25(個)，$
$\overline{x}_{何亮}=\frac {1}{5}\times (24+25+23+26+27)=25(個)，$
$\therefore {S}_{趙明}^2=\frac {1}{5}\times [(25-25)^2+(23-25)^2+\ldots +(21-25)^2]=8，$
${S}_{何亮}^2=\frac {1}{5}\times [(24-25)^2+(25-25)^2+\ldots +(27-25)^2]=2，$
$從方差來看，{S}_{趙明}^2 \gt {S}_{何亮}^2，何亮的成績更穩(wěn)定.$
