已知:
1。有39个乒乓球。其中一个重量异常。其它38个重量正常且相同。
2。工具是一具物理实验室天平,但无法码。
问:称4次,如何找出异常乒乓球,并指出它是过轻或过重。
• n次可称13*3^(n-3)个,并指出它是过轻或过重 -jinjing- ♀ (171 bytes) () 05/02/2010 postreply 06:20:44
• n次可称(3^n-3)/2个,并指出它是过轻或过重。 -康MM- ♀ (68 bytes) () 05/02/2010 postreply 07:24:54
• 康MM的公式正确, 3次只能称12个球,而4次能称39个球. -Blue_Diamond- ♂ (21 bytes) () 05/02/2010 postreply 09:49:20
• 3 times are enough for 13 balls -jinjing- ♀ (263 bytes) () 05/02/2010 postreply 12:30:37
• 回复:3 times are enough for 13 balls -wushuihe- ♂ (93 bytes) () 05/02/2010 postreply 15:39:14
• not big deal,careless,3 times are enough for 13 balls -jinjing- ♀ (273 bytes) () 05/02/2010 postreply 18:03:21
• 回复:not big deal,careless,3 times are enough for 13 balls -wushuihe- ♂ (25 bytes) () 05/03/2010 postreply 01:52:46
• 4 times are enough for4 2 ,but you need 5 times. -Jinjing- ♀ (109 bytes) () 05/02/2010 postreply 14:03:37
• 4 times are enough for 42 balls, you need 5 times. -jinjing- ♀ (168 bytes) () 05/02/2010 postreply 14:12:59
• 回复:4 times are enough for 42 balls, you need 5 times. -康MM- ♀ (123 bytes) () 05/03/2010 postreply 03:59:22
• 答案 -Blue_Diamond- ♂ (3104 bytes) () 05/02/2010 postreply 09:56:02
• 回复:答案 -jinjing- ♀ (175 bytes) () 05/02/2010 postreply 11:26:07
• 回复:答案 -jinjing- ♀ (263 bytes) () 05/02/2010 postreply 12:03:38
• 回复:回复:答案 -jinjing- ♀ (43 bytes) () 05/02/2010 postreply 12:32:38