Question

Aflati numarul rational a stiind ca media aritmetica pomderata a numerelor 10, 15, 20 si x, cu ponderile 4, 3, 5, si, respectiv, 18 este 100.

Answer 1

$a = \frac{10 \times 4 + 15 \times 3 + 20 \times 5 + x \times 18}{4 + 3 + 5} =$
$= 100$
$a = \frac{40 + 45 + 100 + 18x}{12} = 100$
$a = \frac{185 + 18x}{12} = 100$
$185 + 18x = 1200$
$18x = 1200 - 185$
$18x = 1015$
$x = 1015 \div 18$

$x = 56.38$
$a = 56.38$

Answer 2

Am atasat inca o rezolvare !