Solve by equation or formula A and B start from ab at the same time and go opposite each other. When they meet, they are 8 kilometers away from the midpoint of ab. it is known that the speed of a is five sixths of that of B. how many kilometers is the distance between AB and ab?

If the speed of car a is 5 / 6 of that of car B, the speed of car a is 5 / 11 of the sum of the two
8*2/(1-5/11*2)=176

The length of a rectangle is 15 cm more than the width. If the length is reduced by one third and the width is increased by one half, the perimeter of the new rectangle is equal to that of the original rectangle, and the area of the original rectangle is calculated

Let x (1 + 1 / 2) + (x + 15) (1-1 / 3) = x + (x + 15) (3 / 2) x + (x + 15) (2 / 3) = 2x + 15 (3 / 2) x + (2 / 3) x + 10 = 2x + 15 (13 / 6) x-2x = 5

Sixth grade math problems (people's Park marked out a circular.),
The people's Park has a circular fireworks safety zone, covering an area of about 1256 square meters. Can you calculate the diameter of this circular safety zone?
The area of the circular fireworks safety zone in Zhonghua park is about 1962.5 square meters. How long is its diameter than that of the people's Park?

1. The area formula of a circle is s = π R ^ 2 = 1256, if π = 3.14, then R ^ 2 = 400, r = 20
So diameter d = 2R = 40m
2. Similarly, the safe area of China park is s = π R ^ 2 = 1962.5, with a diameter of 50m
50-40 meters longer than the people's Park

Mathematical problem formulation
The number of a is three times less than that of B, and the number of B is one tenth less than that of B, which is four fifths?
Determinant

4/5*10*2-3-4/5*10
=13-8=5

Don't use equations! See the following supplementary questions! Answer in half an hour!
1. If each person borrows four books before the holiday, the last two books will be lost. If the first two people borrow eight books first and the remaining people borrow three books each, these books will be borrowed out. Then how many books are there and how many people borrow them?
2. The school bought several sets of desks and chairs and assigned the students to move them into the warehouse. Among them, two students moved 4 sets each, and the other students moved 5 sets each, so the remaining 12 sets. If each student moved 6 sets, it was just finished. So how many people? How many sets of desks and chairs?
3. Xiao Hong has borrowed a book and must return it on time. If Xiao Hong reads 35 pages a day, she will finish the book one day later than the specified date. If she reads 40 pages a day, she will have to read 5 pages less on the last day. How many days is the deadline? If she reads 39 pages a day, how many pages will she have to read on the last day to finish the book on time?

It can be seen from the title that there are at least three people, at least 19 books, four books for each person, and two less books, so there are 14, 18, 22, 26 books If the first two people borrow 8 books and the rest borrow 3 books, the minimum solution is 22 books and 4 people

Math problems, help, to the formula to answer. Thank you, do not solve the equation
A train from a to B runs 55 kilometers in the first hour and 30% of the whole journey in the second hour, which is more than 5 kilometers from the midpoint. How many kilometers are there between a and B

Distance: (55-5) / (50% - 30%) = 250 km

A mathematical problem, solving equations
In the 400m test, xiao gang ran part of the way at 6m / s, and then sprinted to the finish line at 8m / s, with a score of 1 minute and 5 seconds. How long did Xiao Gang run before sprinting?
I'm not very good at solving equations 】

Let him run x seconds before the sprint
6x+8（65-x）=400
6x+520-8x=400
-2x=-120
x=60
He ran 60 seconds before the sprint
One minute and five seconds equals 65 seconds

40% of a number is 20% less than 3.6. What's the number

Let this number be X
(3.6-40%x)÷3.6=20%
3.6-0.4x=0.72
0.4x=2.88
x=7.2

Subtract 10 from a number, multiply by 2, and add 70 to get 250

Let this number be X,
(x-10)*2+70=250
2x-20+70=250
2x+50=250
2x=200
x=100
That's it

One half of a number is 15 more than 20%. What's the number? Solve the equation

Let this number be x, then
2 molecules, 1 x-20% x = 15
0.5x-0.2x=15
0.3x=15
x=50
A: this number is 50!

Solve by equation or formula A and B start from ab at the same time and go opposite each other. When they meet, they are 8 kilometers away from the midpoint of ab. it is known that the speed of a is five sixths of that of B. how many kilometers is the distance between AB and ab?