P2-PS-170

[Huang Hsin-Yi]

170. 18339-!-item-!-187;#058&011871
For any triangle T in the xy-coordinate plane, the center of T is defined to be the point whose x-coordinate is the average (arithmetic mean) of the x-coordinates of the vertices of T and whose y-coordinate is the average of the y-coordinates of the vertices of T. If a certain triangle has vertices at the points (0,0) and (6,0) and center at the point (3,2), what are the coordinates of the remaining vertex?

(A) (3,4)
(B) (3,6)
(C) (4,9)
(D) (6,4)
(E) (9,6)

Ans:B

請問紅色字部份該怎樣列式子?

[Weichieh]

三角形中心T 被定義為 T 頂點的平均值，這些頂點值是取自各頂點的X座標。
例如三角形T的三個頂點為 （x1, y1）（x2, y2）（x3, y3）
則 the center of T = ( [x1+x2+x3]/3 , [y1+y2+y3]/3 )

[Huang Hsin-Yi]

感謝