有没有好办法？

The sum of the number in each line, column and diagonal in the 3x3 "magic
square" bellow is always constant. Only two numbers are visible.
Which number is missing in field a?

a x x
x x 47
x 63 x

Thanks!

所有跟帖： 

• 回复：有没有好办法？ -duo_duo- ♀ (2 bytes) () 12/30/2009 postreply 11:52:24

• 回复：回复：有没有好办法？ -jinjing- ♀ (38 bytes) () 12/30/2009 postreply 13:16:06

• Yes. Do you have a fast and easy way to explain it? -cma- ♂ (66 bytes) () 12/30/2009 postreply 16:04:31

• 回复：Yes. Do you have a fast and easy way to explain it? -innercool- ♀ (259 bytes) () 12/30/2009 postreply 18:31:12

• 回复：Yes. Do you have a fast and easy way to explain it? -jinjing- ♀ (344 bytes) () 12/30/2009 postreply 18:42:54

• 回复：有没有好办法？ -cma- ♂ (9 bytes) () 12/30/2009 postreply 20:38:40

• 多谢指教. -cma- ♂ (0 bytes) () 12/30/2009 postreply 20:39:40