Question

In clasa a 7 a, media inaltimii celor 11 baieti este de 174 cm, iar media inaltimii celor 16 fete este de 165 cm. Care este media inaltimii elevilor clasei ?

Answer 1

[tex]11+16=27~de~elevi~in~total \\ m_b=174~cm~(media~baieti) \\ m_f=165~cm~(media~fete) \\ m_e= 174+165/{2} \\ m_e=339/2 \\ m_e=169,5~cm(media~elevi) [/tex]

Answer 2

Fie b1, b2, b3,...,b11 inaltimile baietilor.
$\frac{b1+b2+b3+...+b11}{11} =174 => b1+b2+b3+...b11=1914 (cm)$
Fie f1, f2, f3,...,f16 inaltimile fetelor.
$\frac{f1+f2+f3+...+f16}{16} =165 = f1+f2+f3+...+f16=2640 (cm)$
Media inaltimilor elevilor este : $\frac{Suma.inaltimilor.elevilor}{numar.de.elevi}$ = $\frac{b1+b2+b3+...+b11+f1+f2+f3+...f16}{11+16}$ = $\frac{1914+2640}{27} = \frac{x}{y} = \frac{4554}{27} =168,(6) (cm).$