Question

alguem sabe resolver esta questão? ???

Answer 1

$\begin{array}{cccc}Idade&N^o\ Pessoas\ (f_i)&Pt.\ M\'edio\ (x_i)&x_i.f_i\\0 \vdash 10&8&5&40\\10 \vdash 20&1&15&15\\20 \vdash 30&4&25&100\\30 \vdash 40&2&35&70\\\\total&15&&225\end{array}\\\\\\\\ \overline{X}=\dfrac{\sum(x_i.f_i)}{n}=\dfrac{225}{15}=15\\\\\\ S^2 = \dfrac{\sum (x_i-\overline{X})^2.f_i}{n-1}=\dfrac{800+0+400+800}{15-1}=\dfrac{2000}{14}\approx142,86\\\\\\ S=\sqrt{142,86}\\\\ \boxed{\boxed{S\approx11,95}}$

Resposta: A alternativa correta é a letra D (11,25)

Espero ter ajudado.
Bons estudos!