Question

Media aritmetica a nr X si Y este 10,media aritmetica a nr Y si Z este 20,iar media aritmetica a Nr X si Y este 30.Sa se afle media aritmetica a nr X,Y si Z

Answer 1

(x+y)/2=10 => x+y=20 => x=20-y
(y+z)/2=20 => y+z=40=> y=40-z
(x+z)/2=30=> x+z=30=> 20-y+z=30 => -y+z=10 => -40+z+z=10 => 2z=50 => z=25
y=40-z=40-25=15
x=20-y=20-15=5

Answer 2

$\frac{x+y}{2} =10=\ \textgreater \ x+y=10*2=\ \textgreater \ x+y=20 \\ \\ \frac{y+z}{2} =20=\ \textgreater \ y+z=40 \\ \\ \frac{x+z}{2} =30=\ \textgreater \ x+z=60 \\ \\ x+y+y+z+x+z=20+40+60 \\ 2(x+y+z)=120=\ \textgreater \ x+y+z=120:2=60 \\ z=60-20=\ \textgreater \ z=40 \\ x=60-40=\ \textgreater \ x=20 \\ y=60-60=\ \textgreater \ y=0 \\ \\ \frac{x+y+z}{3} = \frac{40+20+0}{3} = \frac{60}{3} =20$