45. A, B and C go to the swimming pool for training regularly. A goes to the swimming pool every four days, B goes to the swimming pool every six days and C goes to the swimming pool every nine days?

It's April 6th
Because the least common multiple of 4, 6 and 9 is 36, that is, 36 days after March 1 is April 6

A and B go swimming, a once every 8 days, B once every 6 days, meet on July 31, what month and what day do they meet?

The least common multiple of ball 8 and ball 6 is 24, so Party A and Party B will meet on August 24

Xiaoming and Xiaojun go to buy books together. Xiaoming takes a fancy to the book 100000 whys, and Xiaojun takes a fancy to science fiction world
If Xiaoming borrows some money to Xiaojun, he will have 10 yuan left. If Xiaojun borrows some money to buy books for Xiaoming, he will have 20 yuan left. It is known that the price of "why 100000" is two-thirds of that of "science fiction world". How much is a copy of "science fiction world"?

Science fiction world (20-10) / (1-2 / 3) = 10 / 1 / 3 = 30 yuan
Have a good time

Is the proportion with unknowns an equation? Right or wrong?

Yes, because the proportion with unknowns is an equation, and the equation with unknowns is an equation

Cosmic solar system Milky way Earth Moon arrangement

Universe (largest) - Galaxy - Solar System - Earth (planet, the third solar system) - Moon (Earth's satellite)

8 plus 72 divided by 4 minus 3 times 5 minus 3 where to add a bracket equals 365

8+72/(4-3)*5-3=365

When a cup is full of water, gently place a small piece of wood on its liquid surface. At this time, the pressure of water on the bottom of the cup will decrease compared with the original____ What's your answer? Why?
The correct answer is the same, but why?

Unchanged ~ wrong title last time, sorry
According to the buoyancy law, the mass of the discharged water is equal to the weight of the floating object
Because the cup is full at the beginning, the water drained out, so the total quality of the things in the cup remains unchanged before and after the wood block is put in
So the pressures are equal
To put it simply, wood blocks replace water equal to the mass of wood blocks, and nothing changes~

2X plus 120 minus 4x equals 100

2x+120-4x=100
4x-2x=120-100
2x=20
x=20÷2
x=10

The two trains run in opposite directions. Car a runs 48 kilometers per hour, and car B runs 60 kilometers per hour. When the two trains go wrong, a passenger on car a starts to count the time when the front of car B passes his window, and it takes 13 seconds for the rear of car B to pass his window______ Rice

A speed: 48 km / h = 1313 M / s, B speed: 60 km / h = 1623 M / s, B vehicle length: (1623 + 1313) × 13 = 390 m; a: the total length of B vehicle is 390 M

If natural numbers a and B satisfy the following conditions: a-1b = 1182, a: B = 7:13, then a + B=______ ．

a: The & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & & nbsp; & & nbsp; & & nbsp; & & nbsp; & nbsp; & nbsp; the & nbsp; & nbsp; & nbsp; & nbsp; the & nbsp; & nbsp; & nbsp; the & nbsp; nbsp; the & nbsp; nbsp; the & nbsp; nbsp; the & nbsp; nbsp; the & nbsp; the & nbsp; nbsp; the & nbsp; nbsp; the & nbsp; nbsp; the & nbsp; nbsp; the & nbsp; & nbsp; & nbsp; & nbsp & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp & nbsp; the & nbsp & nbsp & nbsp & nbsp; & & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp & nbsp; & nbsp; & nbsp; & nbsp; the & nbsp & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; the & nbsp; & nbsp; & nbsp; the & nbsp; & nbsp; & nbsp; the & nbsp; & nbsp; the & nbsp; the & nbsp; & nbsp; the & nbsp; the & nbsp; nbsp; nbsp; nbsp so the answer is: 240

45. A, B and C go to the swimming pool for training regularly. A goes to the swimming pool every four days, B goes to the swimming pool every six days and C goes to the swimming pool every nine days?