【答案】:
5個(gè)
【解析】:
1,$\frac{1}{\sqrt{2}}\approx0.7071$,$\frac{1}{\sqrt{3}}\approx0.5774$,$\frac{1}{\sqrt{4}}=0.5$,$\frac{1}{\sqrt{5}}\approx0.4472$,$\frac{1}{\sqrt{6}}\approx0.4082$,$\cdots$
$1+0.7071=1.7071$
$1.7071+0.5774=2.2845$
$2.2845+0.5=2.7845$
$2.7845+0.4472=3.2317>3$
至少要選5個(gè)數(shù)