AMC8 2001

AMC8 2001 · Q24

AMC8 2001 · Q24. It mainly tests Transformations, Logic puzzles.

Each half of this figure is composed of 3 red triangles, 5 blue triangles and 8 white triangles. When the upper half is folded down over the centerline, 2 pairs of red triangles coincide, as do 3 pairs of blue triangles. There are 2 red-white pairs. How many white pairs coincide?

这个图形的每一半由3个红三角形、5个蓝三角形和8个白三角形组成。当上半部分沿中心线向下折叠时，有2对红三角形重合，3对蓝三角形重合。有2对红白对。有多少对白三角形重合？

(A) 4 4

(B) 5 5

(D) 7 7

(E) 9 9

Answer

Correct choice: (B)

正确答案：（B）

Solution

All six red triangles are accounted for, so the two unmatched upper blue triangles must coincide with lower white triangles. Since one lower white triangle is matched with a red triangle and two are matched with blue triangles, there are five left and these must match with upper white triangles.

所有六个红三角形都已匹配，因此上半部分的两个未匹配蓝三角形必须与下半部分的白色三角形重合。下半部分有一个白三角形与红三角形匹配，两个与蓝三角形匹配，还剩五个，这些必须与上半部分的白三角形匹配。

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