mathematics

圖片參考：http://imgcld.yimg.com/8/n/HA00251295/o/701010070014713873375990.jpg
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2010-10-07 08:39:28 補充：
If you line them up from left to right as volumn 4,3,2,1, then the answer would be 23 cm, which is shown as answer B from the above picture.
But the hint told you it's not 23.

2010-10-07 08:39:54 補充：
Then it must be from left to right as volumn 1,2,3,4. Look at layout A, you should know the answer by looking at the diagram, get it yet ?
If you still haven't get it, read on :

2010-10-07 08:40:04 補充：
When you layout the books as shown in setup A, the first page of volumn 1 is on the right hand side of the book, and last page of volumn 4 would be on the left hand side of the book.

2010-10-07 08:40:12 補充：
A = 0.5 x 2 x 3 + 5 x 2
= 3 + 10
= 13cm