Sixth grade mathematics problems, to process When a runs three eighths of the whole race, B runs one third of the race. After that, a's speed will not change, B's speed will increase. When both of them reach the finish line at the same time, B's speed will increase by ()% It takes 12 hours (including 12 hours) at most for a ship to carry fuel. When it leaves, it travels 30 kilometers per hour. When it returns along the original road, its speed is 8% of that when it goes. How many kilometers can the ship return?

The first question is that V A: V B 1 = (3 / 8): (1 / 3) = 9:8 V A = 9 / 8 V B 1 B before speed up [(1-3 / 8) s] / V A = [(1-1 / 3) s] / V B 2 5 / 8V B 2 = 2 / 3V a

There is a pool, the bottom of the pool has a continuous gushing of spring water, to pump the pool of water, with 12 pumps need to pump 5 hours; with 10 pumps need to pump 7 hours. Ask to pump in 2 hours. At least_____ --Three pumps

A pump is set to pump water x per hour
The spring gushes out every hour
60x-5y=70x-7y
2y=10x
y=5x
There is 60x-5y water in the pool
35x
35 △ 2 + 5 = 22.5 sets
A: 23

A sixth grade math problem (with process)
A cat chases a mouse. The mouse runs along the direction of a-b-c, and the cat runs along the direction of a-d-c. as a result, it catches the mouse at point e. the speed ratio of the mouse to the cat is 17:20, the distance between point C and point E is 3 meters, and the quadrilateral ABCD is a parallelogram. The time spent by the cat and the mouse is equal
How many meters more did the cat run than the mouse to catch up with the mouse?
How many meters is the circumference of the quadrilateral that the cat and mouse run?
Also explain the calculation process

1: The cat ran 3 meters more than C, and the mouse ran another 3 meters to C,
As a result, the cat ran six meters more than the mouse
2: Let the cat's speed be 20, the mouse's speed be 17, and the speed difference be 20-17 = 3
6 / 3 = 2, so the perimeter of quadrilateral is 2 * (17 + 20) = 74m

Concentration 1. What is the mixed concentration of 500 g of 70% alcohol solution and 300 g of 50% alcohol solution? 2. The two trains run from two places 500 km apart at the same time, but they haven't met after 4 hours, but the difference is 20 km. It is known that the train a runs 65 km per hour, and the train B runs how many km per hour?
Write the specific calculation process

1)(500*0.7+300*0.5)/(300+500)=0.625=62.5%
2) It is set to travel XKM per hour
65*4+4x+20=500
260+4x+20=500
4x=220
x=55km

For a project, Party A and Party B work together for 4 days, and then Party A works alone for 6 days to complete all tasks. Given that Party A has completed 1 / 80 of the project every day, how many days will it take for Party A and Party B to complete the project alone?

Let B finish in X days, then B does one part of X every day, and a does one part of X every day (1 part of x plus 1 part of 80). We can establish the equation (1 part of X + 1 part of 80 + 1 part of x) multiplied by 4 + (1 part of X + 1 part of 80) multiplied by 6 = 1 = (2 part of x plus 1 part of 80) multiplied by 4 + (1 part of X + 1 part of 80) multiplied by 6 = 14 part of X + 1 part of 8 = 1, and then x equals 16

There is a book which is divided into two volumes. The first volume has nine more pages than the second volume. The total number of pages in this book is 2007. For example, 105 = 1 + 5 = 6. Find the number of pages in the first volume
For example, if the first volume is 19 pages and the second volume is 10 pages, then the sum of pages is 1 + 2 + 3+_ +9+1+2+_ +10 (Volume I) + 1 + 2 + 3+___ 9 + 1 (Volume II) = 146

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 451 + 1 + 1 + 2 + 1 + 3 + 1 + 4 + 1 + 5 + 1 + 6 + 1 + 7 + 1 + 8 + 1 + 9 = 55 and so on. The total number of pages within 100 is 45 + 55 + 65 + 75 + 85 + 95 + 105 + 115 + 125 + 135 = 900. The total number of pages within the second 100 is 900 + 100 = 1000 (each page has one more 100 digits)

Number a is 3 / 2 of number B, and number B is 5 / 4 of number C. what is the ratio of number a to number C?

15/8

2005 minus 0.5 times, and then minus the remaining 0.33333 And then subtract the remaining 0.25 times. If you go on like this, subtract the remaining 0.0002005 times. How much is left?
Finally, subtract the remaining 1 / 2005

2005*（1-1/2）（1-1/3）（1-1/4）…… （1-1/n)
=2005*1/n
This problem is irregular, because 0.0002005 cannot write 1 / n
If it is reduced to 1 / 2005, then
2005*（1-1/2）（1-1/3）（1-1/4）…… （1-1/2005）
＝2005*1/2*2/3*3/4*…… 2004/2005
All of them are in the middle
＝2005*1/2005
＝1

The price of a windbreaker is reduced by 20% and then by 20%. The price after two reductions is 64 yuan. How much is the original price?

It's 100 yuan
The second price reduction is 20% lower than the price after the first price reduction, so the price after the first price reduction is 64 ／ 20% = 80, and the original price is 80 ／ 20% = 100

The ratio of the number of boys to girls in a primary school class is 8:7, and there are 7 girls. At this time, the number of girls is 7 / 6 times of that of boys. How many boys are there in this class?

There are 8x boys and 7x girls
7x + 7 girls after transfer
The number of boys is six times that of girls
7x+7=8x*7/6
x=3
A: Boys 3 * 8 = 24, Girls 7 * 3 = 21