There are 12 numbers on the clock face: 1, 2, 3, 11, 12

First of all, let me tell you, there is no skill in this topic at all, and then how to put it bluntly or make up.

First question. Because 1+2+3+......12=78。

So, all you have to do is make up a few numbers so that the sum of them is 39, and then add a negative sign to those numbers, or the rest of them.

Why is there no pattern, you see

12 + 11 + 10 + 6 (then of course, the remaining 9,8,7,5,4,3,2,1 is also a group.) )

12+11+9+7 group.

12+10+9+8 group.

11+10+9+8+1 and so on and so forth.

But 12 can be split into 3+9, 4+8, 5+7, so there is no rule to follow at all. In short, you can list as many groups as you want, and the only way to calculate the total number is to list them all. I believe that you will be given 1 hour, there is still hope to finish the list, be careful not to miss or repeat it...

That's why the person who came up with this question likes to play tricks).

Second question. (The meaning of the title should be to add a minus sign before all the numbers clamped by the hour and minute hands...) Otherwise, I don't know how many kinds. ）

For example, in the first question, it is sufficient to make the sum of consecutive numbers 39.

Then, to be consecutive, there are only 4, 5, 6, 7, 8, 9 and 12, 11, 10, 1, 2, 3 in this case

It's easy to see.

3, 4, 5, 6, 7, 8, 9 between 9:15 and 9:20

and between 3:45 a.m. and 3:50 a.m., 10, 11, 12, 1, 2, 3

Just add a negative sign to the front.

2) No, you can't.

3), time when the sum is 39 plus a minus sign.

4) The rule is to find the sum of all the numbers, if (the sum is 2), you can use the sum of some of these numbers to get it.

2) No. 3) 1-2-3+4=0 4.01 or 12.21.

2-3-4+5 5.06 or 1.26.

3-4-5+6 6:11 or 2:31.

5-6-7+8 8:21 or 4:41.

Wait. 4) Forehead ......

It should be a "symbol" instead of a "minus".

There are 12 numerals on the clock face, and the time it takes for the hour hand to travel over two adjacent numerals is 1 hour.

The process is as follows:

1) The schematic diagram of the clock dial is as follows:

2) The dial of a clock has 12 numbers on it, and these 12 numbers divide a circumference into 12 equal parts.

3) For the hour hand, the time to walk in one circle is 12 hours, then the time between two adjacent numbers is: 12 12 = 1 hour.

2 -3 4 -5 6 7 8 -9 -10 11 -12

2. No, because the original sum is 78, which is an even number, and changing any number to a negative number is equivalent to the sum minus twice the number, which must be an even number.

-1+2+3-4-5+6+7-8-9+10+11-12=0

Yes, 1+....12=13 6=78, any odd symbol can be changed.

Find 1, 2, 3, 4, 5 ,... first, 12 The sum of these 12 numbers is 78, and the sum of the absolute values of 5 negative numbers is 39 when 78 2 is obtained, and the sum of the absolute values of 5 numbers in the 12 numbers is equal to 39 in the book Tong Chonghong can be judged by adding a negative sign in front of the Hong

So there are: (1) 1+2+3+4+5+....+12 = 78,78 2 = 39,1 + 6 + 9 + 11 + 12 = 39, 5 numbers are 1, 6, 9, 11, 12 (the answer is not unique).

1) That is, five digits and a minus sign in front of 39.

a 4,6,7,10,12

b 5,6,7,9,12

c 3,6,7,11,12

d 3,6,8,10,12

2) The sum of the five numbers is 39

2) Rule: Add a negative sign in front of the sum of five numbers to 39.

Solution: (1) 1 2 3 5-4+6 7 8 9+10+11+12

2) Rule: Calculate the sum first, take half, add a positive sign before the sum of half of the number, and add a negative sign before the rest of the number.

There are 12 numbers on the cover, and the time that the hour hand passes through the two adjacent numbers is generally bounded by 5 minutes, and each scale is one minute.