Toán khó vòng 9

B

braga

Theo đề bài ta có:

$1+2+3+4+...+n=190$ \Rightarrow $\dfrac{n(n+1)}{2}=190$ \Rightarrow $n(n+1)=380$ ma 380=19.20 \Rightarrow $n=19$

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C

chienhopnguyen

Mot tong cua n so tu nhien lien tiep , bat dau tu 1 bang 190. Hay xac dinh n
GIAI GUIP MINH NHA CAM ON NHIEU !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!: D
se la:1+2+3+...+190=n
vay ta co cong thuc tinh nhu sau:
(1+190).{(190-1):1+1}:2=n
191.95=n
18145=n
vay n=18145.
ssssssssssss
ssssssssssss
neu dung thi thanks to nhe!

:p;):D
 
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