This math problem is so difficult, please teach me

The original ratio is 7:5, that is, the elder brother accounts for 7 12, the younger brother accounts for 5 12, and the elder brother has 2 12 = 1 6 more than the younger brother.

The current ratio is 3:4, i.e., the elder brother accounts for 3 7, the younger brother accounts for 4 7, and the elder brother has 1 7 less than the younger brother.

The elder brother gave the younger brother 520 yuan, and the total number of the two remained the same, but the gap narrowed by 520 * 2 = 1040 yuan.

The proportion of the decrease is 1 6 + 1 7 = 13 42

So the total number of the two brothers is 1040 (13 42) = 3360 yuan.

Therefore, now my brother has 3360 * (3 7) = 1440 yuan.

If the elder brother originally had x dollars, then the younger brother had 5 7x dollars.

From the inscription: x-520 (5 7x+520)=4:3: x=1960

So, my brother is rich now: 1960-520=1440 yuan.

My brother used to have a total of 7 12 and later became 4 7

So the total amount of money is 520 (4 7-5 12) = 3360 (yuan), it turns out that the elder brother has 1960 yuan and the younger brother has 1400 yuan.

Later, the elder brother had 1440 yuan, and the younger brother had 1920 yuan.

It turned out that the brother's money accounted for the total number of the two.

Now the brother's money accounts for the total number of the two.

Shared by two. 520 (7 12 3 7) 3360 yuan.

Now my brother has.

3360 3 7 1440 yuan.

Solution, let it be that the younger brother has x yuan and the elder brother has y yuan.

y:x=7:5 (1)

y-520:x+520=4:3 (2)

The solution is x=18200

y=25480

My brother now has 25,480-520=24,960 yuan.

If the elder brother is 7x, then the younger brother is 5x

7x-520)/(5x+520)=4/3

7x=25480，5x=18200

Solve the equation: x:y=7:5

x-520):(y+520)=3:4

Brother x = 1960

Now brother x-520 = 1440

7 12*x-3 7*x=520 (according to the equation of the change of the elder brother's money) x is the total amount of money.

x=3360

The elder brother now has 1440

Because 7 15 105

100 Mingfeng 98 2 , so subtracting Zihuai Xian 7 from 100 consecutive beats, the minimum positive number obtained is 2

There is a problem with this question itself, it seems to be logical but it is actually a wrong question, 27 can not be added 2, 2 yuan is part of 27 yuan, how to add it well, 3 people spent 9 + 9 + 7 = 25, 25 is earned by the boss, and the other 5 is fast is the other 2 people take 1 yuan each, and one person divides 1 yuan to hide two yuan, 1 + 1 + 1 + 2 = 5, so 5 + 25 = 30, it is impossible to get 29.

Laid daily.

The campus network is long.

300 3 20 2000 meters.

Good luck with your studies!

Hope it helps.

Thank you!

If the worker lays 60% of the total length in 4 days, then one day is 60% of the total length 4=15%.

Then, for a total of five days, it is 5*15%=75% of the total length, which is 300 meters.

So, the overall length is 300 75% = 400 meters.

2000m

One day is 300m, four days is 1200m, and 1200m is 60% of the total length

It doesn't take 10 minutes...

Number the holes as shown below...

Set the farmer's number as A, B, C... In the initial state, A accounts for 4, B accounts for 5, and C accounts for 6.

1min: B to 2

2min: None of them move.

3min: B back 5

4min: B to 8

5min: No movement. (If the gopher is not found at this time, the gopher must be in the 2nd place.)

6min: B back 5(Gopher in 1, 3).

7min: None of them move. (Gopher back 2).

8min: A to 1, C to 3(Catch the gopher).

Each hole is numbered as follows:

The first minute check 135 at this point the rat can only be in the 246789 and the next minute all but 2 holes are possible.

The second minute, check 468, at this time, the mouse can only be at 13579 (the possibility of 2 has been ruled out), and in the third minute, still check 468, if the mouse is not found, it means that the mouse is not at 79 in the last minute, and can only be at 135, so it can only run from 135 to 2 at this moment

The fourth minute can only be at 2 in the last minute, so you can only run from 2 to 135 at the moment, so let's stay at the 135 hole!

A total of 4 min to find mice.

Up to 4 minutes.

Defend 468 first, and if the gopher appears at 5, wait another 1 minute, so that it can change its position next time to catch it; If it appears at 79, it will be caught directly in the next minute; If it appears at 13, it will be changed to 246, and you will be able to catch it in the next minute. Opening number.

It's not that hard... Just look for the holes in the four corners, and then add the hole in the middle, and you're done, and see where it goes.