Question

一道英语奥数题

If you continue the given number pattern, in what row and in what position in that row will the number 320 be?
1 -------------- row 1
2 3 -------------- row 2
4 5 6 -------------- row 3
7 8 9 10 -------------- row 4
The answers are given in the order of row ; position.

请给解题思路，谢谢！

Answer 1

第n排有n个数，且个相邻排数的个数构成等差数列，则前n排共有（n+1）*n/2个数，令（n+1）*n/2=320求出n，得24点多，意味着320在25排里，二（n+1）*n/2中n取24时等于300，即24排最后个数是300，而25排最后为300+25>320，则320在25排第20个数
row 25
position 20