Uncle Zhang and Aunt Li donated 1800 yuan to the Sichuan disaster area on average. The ratio of Uncle Zhang and Aunt Li's donation is 8:7. How much yuan can Aunt Li donate? Do you have a higher IQ than the sixth grade students```

Uncle Zhang and Aunt Li donated 1800 yuan to the Sichuan disaster area on average. The ratio of Uncle Zhang and Aunt Li's donation is 8:7. How much yuan can Aunt Li donate? Do you have a higher IQ than the sixth grade students```

In fact, it's very simple. The average person donates 1800 yuan, that is, a total of 3600 yuan
1800 × 2 = 3600 yuan
8 + 7 = 15 (number of shares) 7 △ 15 = 7 / 15 (what percentage of Aunt Li's contribution to the total score
(a few tenths)
3600 × 7 / 15 = 1680 yuan
I'm in the sixth grade, too

Sichuan Ya'an earthquake, our school donations, two times, students donated 60000, teachers donated 30000 yuan
After the Ya'an earthquake in Sichuan Province, our school donated 60000 yuan to students and 30000 yuan to teachers. It is known that the number of students is 20 times that of teachers, but the per capita donation of teachers is 180 yuan more than that of students. Q: how many teachers and students are there in our school?

150 teachers, 3000 students, a total of 3150, right?

The difference between a and B is 80. 1 / 2 of a is equal to 2 / 3 of the total. What's the difference between a and B

Let a and B be x and Y respectively
x-y=80 (1)
x/2=2y/3 (2)
From (2) * 6
3x = 4Y, i.e
3x-4y=0 (3)
From (1) * 3 - (3)
Y = 240, substituting (1) gives x = 320
A: the numbers of a and B are 320 and 240 respectively

If the 14th power of 5 - the 3rd power of 25 is a multiple of the nth power of 2 (n is a positive integer), find the maximum value of n

5^14-25^3=5^6（5^8-1）=5^6（5^4-1）（5^4+1）=5^6*624*626=5^6*39*16*313*2
The maximum value of n is 5

On a straight road, a car is driving at the speed of V1 = 90 km / h, and a truck in front of it is driving at the speed of V2 = 72 km / h,
On a straight road, a car runs at the speed of V1 = 90 km / h, and a truck in front of it runs at the speed of V2 = 72 km / h. When the distance between them is △ X1 = 200 m, the car turns into the overtaking lane and starts to overtake with the acceleration of A1 = 2 m / S2. The maximum speed of the car is controlled at VM = 108 km / h. When the car and the truck are parallel, the truck decelerates with the acceleration of A2 = 1 m / S2, When the car exceeds the truck △ x2 = 22 m, it turns back to the lane, and the overtaking process ends. Find (1) the time from the car ready to overtake to parallel with the truck; (2) the time from the car ready to overtake to parallel with the truck
(2) The distance from a car running in parallel with a truck to completing overtaking

（1）.20.625（2）.60m
(1) The car speed is converted from 90km / h to 25m / s, and the maximum speed is converted from 108km / h to 30m / s
The speed of freight car is converted from 72km / h to 20m / s
Let the acceleration time be T1
Vm=v1+a1*t1 30m/s=25m/s+2m/s2*t1 ∴t1=2.5s
Let the time from overtaking to parallel be T2, and the displacement of freight car be x2
x2=v2*t2
The car displacement is X1 = (VM square - V1 square / 2A1) + VM (t2-t1)
X1 = x2 + △ X1 algebra, T2 = 60.625
(2) Set the time from parallel to overtaking completion T3
Trolley displacement X3 = VM * T3
Freight car displacement X4 = square of v2t3-1 / 2A2 * T3
From the problem, we can see that x3-x4 = △ x2 algebra gets T3 = 2S
∴x3=60m
You are welcome

It is known that the lengths of three sides a, B and C of triangle ABC satisfy AA + BB + CC + 338 = 10A + 24B + 26c. Try to judge the shape of triangle and explain the reason

a²+b²+c²+338=10a+24b+26c
a²-10a+25+b²-24b+144+c²-26c+169=0
(a-5)²+(b-12)²+(c-13)²=0
a-5=0,a=5
b-12=0,b=12
c-13=0,c=13
a²+b²=5²+12²=169
c²=13²=169
a²+b²=c²
So it's a right triangle

At the same time, the passenger train and the train leave from a and B. when they meet, the distance ratio of the passenger train and the freight train is 5:4. After meeting, the freight train is 15 times faster than the passenger train per hour
Km, the bus is still at the same speed, the result of the car at the same time arrived at the other party's departure station. Given a total of 10 hours of freight cars, how many kilometers is the distance between a and B? Process? Using fractional application solution is not an equation

The speed ratio of the bus to the train is 5:4, and the speed difference is 15,
Then the bus speed is 5 * 15 = 75 and the train speed is 4 * 15 = 60
The bus also runs for 10 hours, distance = 75 × 10 = 750
The distance between a and B is 750 km

In geometry, what is "projection" and what is its application?

Projective geometry is the study of projective properties of figures, that is, their invariable properties after projective transformation. It was once also called projective geometry. In classical geometry, projective geometry is in a special position, through which other geometries can be connected
Some contents of projective geometry had been discovered before B.C. based on the needs of drawing and architecture, ancient Greek geometricians began to study perspective, that is, projection and interception. However, it was not until the 19th century that an independent system was formed and tended to be complete
In 1822, the French mathematician Poncelet published his first systematic work on projective geometry. He was the first mathematician to realize that projective geometry is a new branch of mathematics
Projective geometry is widely used in aviation, surveying, drawing and photography

Two cars set out from a certain place at the same time to transport a batch of goods to the construction site 165 kilometers away. Car a arrived 0.8 hours earlier than car B,
When car a arrives at the destination, car B is 24 kilometers away from the destination. How long does it take to drive the whole journey?

When car a arrives at the destination, car B is 24 kilometers away from the destination and needs to drive for 0.8 hours,
It can be concluded that the speed of vehicle B is 24 △ 0.8 = 30 km / h, and the whole journey takes 165 △ 30 = 5.5 hours,
Therefore, it takes 5.5-0.8 = 4.7 hours for car a to drive

5. - 10.15. - 20.25. - 30.35. - 40.45. - 50
How to calculate the 100th number
The 99th one, too

Let's look at this sequence first of all, let's put aside its minus sign
Each of his items is a multiple of 5, and the multiple is the number of his items
So the 99th is 99 × 5 = 495
The 100th is 100 × 5 = 500
Then consider the symbols
Odd items are positive and even items are negative
So item 99 is 495 and item 100 is - 500