Super difficult math problems for 6th grade! Hurry!!

Answer: After getting this kind of question, it is to add up all of them, which has become a habit, but after adding up this question, I found that the existing ones are counted 3 times, and some are 2 times, and I don't know how many times to divide it by! After careful observation, it turns out that it is actually 2,4,5 squads that are counted 2 times, but the efficiency of these three teams is known to us, so adding a 2,4,5 is not all counted 3 times?

So the sum of the efficiency of the five squads is: (1 12 + 1 7 + 1 8 + 1 42 + 1 8) 3 = 1 6, so it takes six days for the five squads to work together to complete the project.

A small squad x days.

Two squads y day.

Three squads z day.

Four squads for M days.

Five squads n days.

1/x + 1/y +1/z= 1/12

1/x + 1/z+ 1/n=1/7

1/y+ 1/m + 1/n= 1/8

1/x+ 1/z +1/m=1/42

Then count again.

1 x+1 y+1 z+1 m+1 n will do.

You see if you have made any mistakes in your question, and I will slowly calculate it for you.

1 (25) ton is 1 5,60 m less than 20 t 1 5,60 m less than (90) 1 3

2 The price of a refrigerator is now 1 10 lower than the original price, here (the original) is regarded as "1", and the current price is the original (9) (10).

3. The upper bottom of a trapezoidal shape is 1 6, the lower bottom is 1 5 meters, the height is 1 2 meters, and its area is (11 120) square meters.

4. A section of wood is 6 meters long, the first time it was used 1 3, the second time it was used 1 3 meters, and there were (11 3) meters left.

Second, the calculation should be simple if it can be simple.

3. Solve the problem.

1. A bottle of drink, the first time to pour out the total number of 1 2, the second time to pour out the total number of 1 3, there are still 50 ml left, how many ml of this bottle of drink was original? （1-1/2-1/3）*x=50 x=300

2. The turnover of Parkson Mall in the first quarter was 52 million yuan, an increase of 1 10 in the second quarter compared with the first quarterWhat was the turnover in the second quarter? 5200*（1+1/10）=5720

3. Build a 500-meter-long canal, which has been repaired to a total length of 2 5, how many meters are left to be repaired? 500*（1-2/5）=300

4. The students planted trees in Qianling Mountain, 3 8 of the total number were planted on the first day, 1 3 3 were planted on the second day, 360 more trees were planted on the first day than on the second day, how many trees are there in this batch? （3/8-1/3）*x=360 x=8640

20(1+1/5)=24 60/(1-1/3)=90

Original price 9 10

50 (1-1 2-1 3) = 50 (1 6) = 300 ml 5200 * (1 + 1 10) = 5200 * 11 10 = 57.2 million yuan 500 * (1-2 5) = 500 * 3 5 = 300 meters 360 (3 8-1 3) = 360 (1 24) = 8640 pieces.

1: (24) tons, (90) meters.

2: (original price), (9) (10).

3: (11,120) square meters.

4: (11 3) m.

Two: 5 8 10 9-5 8 = 5 72

3 4-1 2-3 8) 5 8 = (-1 5) three: 1:50 (1-1 3) (1-1 2) = 150 ml 2:

5200 * (1 + 1 10) = 57.2 million yuan 3: 500 * (1-2 5) = 300 meters.

4: 360 (3 8-1 3) = 8460 trees.

The third question: 1: 50 divided by 1-half plus one-third = 300 ml 2: 5200 times 1 plus one-tenth = 57.2 million yuan.

3: 500*(1-2 5) = 300 meters.

4: 360 (3 8-1 3) = 8640 (tree).

Elder brother.. Your question... It's excellent.