Do điểm trung bình bằng 6,8 nên :
5⋅2+6⋅5+9⋅n+10⋅12+5+n+1=6,85⋅2+6⋅5+9⋅n+10⋅12+5+n+1=6,8
9⋅n+50n+8=6,89⋅n+50n+8=6,8
⇒9⋅n+50=(n+8)⋅6,8⇒9⋅n+50=(n+8)⋅6,8
⇔9⋅n+50=6,8⋅n+54,4⇔9⋅n+50=6,8⋅n+54,4
⇔9⋅n−6,8⋅n=(−50)+54,4⇔9⋅n−6,8⋅n=(−50)+54,4
⇔2,2⋅n=4,4⇔2,2⋅n=4,4
⇒n=2
k mk nhá
Ai k mk,mk k lại
HC TỐT
#TTV#
Bài giải
Ta có: \(\overline{X}\) =\(\frac{5.2+6.5+9.n+10.1}{2+5+n+1}\)
\(\overline{X}\) =\(\frac{50+9.n}{8+n}\)
6,8= \(\frac{50+9.n}{8+n}\)
50+9.n=6,8(8+n)
50+9.n=54,4+6,8
9n-6,8n=54,4-50
2,2n=4,4
n=4,4:2,2
n=2