Question

fiind date trei numere se stie ca media aritmetica a primelor doua numere este 1,4 ; media aritmetica a ultimelor doua numere este2 ,iar ultimul numar este de 4 ori mai mare decat al doilea.sa se afle numerele si media aritmetica

Answer 1

(a+b)/2=1.4
(b+c)/2=2
c=4b
a+b=2.8
b+c=4
4b+b=4
5b=4
b=4/5
b=0.8
c=4×0.8
c=3.2
a+b=2.8
a+0.8=2.8
a=2
(a+b+c)/3=(2+0.8+3.2)/3=6/3=2

Answer 2

$ma_1=1,4 \\\\ ma_1=\frac{a+b}{2} \\\\\\ \frac{a+b}{2}=1,4 \\\\ a+b=2*1,4 \\\\ \underline{a+b=2,8} \\\\\\ ma_2=2 \\\\ ma_2=\frac{b+c}{2} \\\\ \frac{b+c}{2}=2*2 \\\\ \underline{b+c=4} \\\\\\ \boxed{c=4b} \\\\\\ b+4b=4 \\\\ 5b=4 \\\\ \boxed{b=\frac{4}{5} \to 0,8} \\\\ c=4*0,8 \\\\ \boxed{c=3,2} \\\\ a=2,8-0,8 \\\\ \boxed{a=2} \\\\\\ ma_3=\frac{a+b+c}{3}=\frac{2+0,8+3,2}{3} =\frac{\not 6}{\not 3} \longrightarrow \boxed{ma_3=2}$