When it comes to the first year of junior high school math problems, come to the masters!

There are two solutions:

Obviously, there is no discount for the part of 80 yuan, because at least 100 yuan must be more than 100 yuan to be discounted, that is, the payment after the discount should be more than 90 yuan, which does not match the conditions of the topic. The 252 yuan may be 100-300 yuan after the 9% discount, or it may be the result of more than 300 yuan discount, so there are two situations.

Because 252 <300, the original price should be 280 + 80 = 360 yuan, so after being combined according to the 20% discount, the ** is 360 * yuan;

Because 252 >300, the original price should be 315 + 80 = 395 yuan, so after being combined according to the 20% discount, the ** is 395 * yuan OK, so easy

There is no discount for $85 items.

243 90% = 270 yuan.

243 80% = yuan.

In other words, 243 yuan may be 9% off or 8% off.

If you get 9% off. The total price is 270 + 85 = 355 yuan.

You can get a 20% discount = 355 * 80% = 284 yuan.

If you get a 20% discount. The total price is:

Twenty percent discount = 311 yuan.

The original price should be 280 + 80 = 360 yuan, and after being combined according to the 20% discount, the ** is 360 * yuan;

The original price should be 315 + 80 = 395 yuan, and after being combined according to the 20% discount, the ** is 395 * yuan.

Hands up, hope it helps!

(1) If the passenger is transported back and forth by car alone.

It must be sent three times, and 4 people must be sent each time.

40 5 60 = 3 and 1 3 (hours) > 3 hours If the passenger is sent back and forth by car alone, try to illustrate that the probability of getting all 12 passengers to catch the train is 0 (2) If the rest of the people can walk for a while by car, it is possible to catch the train for a while, and the speed of walking is a kilometer per hour, and the car will send each person x kilometers, then each person will walk (40-x) kilometers.

x-(40-x)]/60=[(40-x）/2]/a (1)x/60+(40-x)/a<=3 (2)

The solution gives a>=2,5

That is, you can catch a train by walking at a speed of kilometers per hour or more.

If the walking speed is 5 kilometers per hour, the time required is 1 hour and 35 minutes.

Four people took the first ride to 30 kilometers, which took 30 minutes, and the next two and a half hours the five people walked to the station by themselves.

Then drive back, of course the remaining 8 people will walk 3 km (because it takes 27 minutes to drive back). Then the four of them were hitchhiking, it took 31 minutes to get to 34 kilometers, and the remaining 6 kilometers took the next 1 and a half hours, walking on their own.

Then in the drive back, the last 4 people had already walked about 8 kilometers (because it took 26 minutes to get back) and then used the rest of the time to get them to the station.

(1) Assuming that a passenger is transported by car, it will take 3 hours and 20 minutes to pull the passenger if the passenger does not move at all.

But if these passengers are in a hurry, I think they will definitely walk on their own while the car starts, then the time required should be: 1 hour and 15 minutes + 1 hour 5 minutes and seconds + 30 minutes and seconds, obviously, the sad passengers have caught the train... At the same time, this is also the answer to the second question.

Covered integer dots include: -3, -1, 2, 3

A wooden strip of length 3 can cover up to 4 integer points. 3 lengths with a spacing of 1, plus the number of the endpoints, is exactly 4.

The rise of the water surface in centimeters indicates the volume of the cone v=

Since the cone volume v=1 3* *20 h

So 1 3* *20 h=

>h=18cm

40 square times =y y is the volume of the cone 20 square times x=y

20 square times x = 40 square times .

This can be solved to x=4, which is 4 centimeters high.

Calculate the increased volume first, according to which the increased volume is equal to the volume of the cone.

The solution is h=

Base area = 1 2 40 20 square centimeters).

The volume of the cone is 1 3 20 cubic centimeters).

The height of the cone is 10 1 3 20 = 3 2 cm

The rising volume of water is v= 40 40 , which is equal to the volume of the cone, so the height is the volume 3 of the base area of the cone. i.e. high is 40 40

Not a right triangle is: 4

An outer angle is equal to an inner angle adjacent to it.

The water rises and the volume of the cylinder is 40 * the volume of the cone = 1 3 * 40 * high.

Height = cm.

Total water volume: 40 * 40 * * 80 = 401920 cubic centimeters of water rises, cone.

The volume is equal to the volume of the rising water:

Volume after rising water: 40 * 40 * * 80 + volume = 409456 cubic centimeter cone volume: 409456-401920 = 7536 cubic centimeters and higher than: 7536 ( *40*40 3) = centimeters.

The part of the water that rises is the volume of the cone, and the height of the cone is calculated to be (*1600*cm).

Cone volume.

bai = base area du * height 3

Bottom area zhi

DAO = Volume = 1256 * High 3

Cylindrical volume = base area * height = PAI * 40 2 * 80 = 401920cm 3 Add cone.

Post-body volume = base area * height = PAI * 40 2 * (80 + volume increase = 409456-401920 = 7536cm 3 = conical volume so: 1256 * height 3 = 7536

Height = 7536 * 3 1256 = 18cm

The diameter of the cone is 40, so the radius is 20Don't get it wrong, don't say that others write nonsense, do the math yourself!

The volume of the cone = 40

The base area of the cone = (40 2) = 400

So the height of the cone = (3 2400) 400 = 18cm

1/3π*20^2*h=π*40^2*

The solution is h=18

The height of the cone is 18 cm.

The first, the third, the fifth, 、......The odd number of the first is arranged: 2, 4, 6, 8, 10 ,......

The second, fourth, and sixth 、......The arrangement of the even number: -1, -1, -1,......

The 199th in this sequence is 2, 4, 6, 8 ,......(199+1) 2=100.

A: Yes 200

The even numbers are -1

The odd number is a series of equal differences.

The first term is 2 and the tolerance is 2

199 is equivalent to the 100th term in the series of equal differences.

So the 199th number is 200

Two is a group, (2n, -1).

So 199 is the first number of the 100th group.

So it's 2 times 100

According to your sequence, the number -1 is the 200th number, and 198 is the 199th number.

No points、、、

It can be seen that the 'odd number' is a multiple of 2.

Even numbers' are -1

199 should be 199x2 = 398