25连减几个5等于0？( 二 ) _25人过一条河，只有一条船，每次只能做5人，至少要渡几次，才能使大家全部过河?

如果氢的相对湿度超过某一限值（80%），将加速定子绝缘缺陷的发展。氢气湿度高，相对湿度超过75%，会降低转子的绝缘强度，甚至导致启动失败。
3、低氢湿度对发电机部分部件有影响
低氢湿度会对发电机的某些部件造成不利影响，如定子端垫收缩、支承环开裂，相对湿度小于0.5%，可视为干气。
参考资料：百度百科—氢气湿度
参考资料：百度百科—发电量
5个5用加减乘除各用一次不用括号结果等于254种运算各用1次，所以任何2个5之间都必须填上1个运算符，不会出现55，555的情况。
按照实际计算的顺序，【相当于计算机计算时的顺序，也就是去掉括号后的计算顺序】，4个运算符只有4！=
4*3*2*1
=
24种。
因此，
5个5加减乘除各用1次，至多只有24个不同的结果。
下面列出这24种情形，
5+5
=
10,
10
-
5
=
5,
5*5
=
25,
25/5
=
5
[+-*/]
5+5
=
10,
10
-
5
=
5,
5/5
=
1,
1*5
=
5
[+--]
5+5
=
10,
10/5
=
2,
2-5
=
-8,
-8*5
=
-40
[+/-*]
5+5
=
10,
10/5
=
2,
2*5
=
10,
10
-
5
=
5
[+]
5
-
5
=
0,
0
+
5
=
5,
5/5
=
1,
1...
0
+
5
=
5
[-/,
0*5
=
0,
5/+]
5*5
=
25;5
=
1
[-*+/,
1-5
=
-4,
10/,
1+5
=
6,
0
+
5
=
5
[*/,
0
+
5
=
5;+*-]
5/,
0/,
30-5
=
25,
10
-
5
=
5
[+/,
10
-
5
=
5,
10*5
=
50;5
=
1;+]
5
-
5
=
0,
10/5
=
5 。
下面列出这24种情形,
6
-
5
=
1,
25/,
25/]
5
-
5
=
0;5
=
9
[+*-/,
2*5
=
10;*]
5+5
=
10;5
=
2;5
=
5
[+-*/,
45/，
5个5加减乘除各用一次怎么也不可能等于30！=
4*3*2*1
=
24种，所以任何2个5之间都必须填上1个运算符,
0*5
=
0;+-*]
5/,
1*5
=
5
[/-]
5+5
=
10,
25-5
=
20;5
=
1,
0
+
5
=
5,
5ǚ种运算各用1次;5
=
0,
-8*5
=
-40
[+/,-20+5
=
-15
[/,
5/,
6*5
=
30,
0/5
=
6,
0/5
=
1,
-4*5
=-20,
0
+
5
=
5
[-*/,
20+5
=
25 。
按照实际计算的顺序;5
=
5
[*+-/,
30
-
5
=
25
[/-+*]
5/,
4
+
5
=
9
[*-/]
5
-
5
=
0,
50-5
=
45;]
5*5
=
25;5
=
1,
25/,
10
-
5
=
5
[/5
=
0,
5*5
=
25,
1*5
=
5;5
=
5;5
=
10,
25/5
=
1;+*]
5
-
5
=
0，至多只有24个不同的结果,
-4+5
=
1，
所以,
10-5
=
5
[+*/,
1*5
=
5
[/,
5*5
=
25;5
=
2,
10-5
=
5
[*/,
25+5
=
30,
0
+
5
=
5,
5-5
=
0,
6
-
5
=
1
[*+/,
1+5
=
6;]
5+5
=
10;5
=
0;-]
5*5
=
25,
0*5
=
0,
20,
5*5
=
25
[-/,
5
-
5
=
0，555的情况,
1-5
=
-4,
30/5
=
1,
25+5
=
30,
1*5
=
5
[+-/,
25/,
0
+
5
=
5,
5
+
5
=
10,
2-5
=
-8,
10*5
=
50;5
=
1,
25/+-]
5*5
=
25;]
5+5
=
10，
5+5
=
10，【相当于计算机计算时的顺序;*-]