The current price of Andersen's fairy tales is 20 yuan, 1 / 6 lower than the original price. How much is the original price?

twenty-four

Xiao Ming bought a set of Andersen's fairy tales and paid 74.8 yuan. It is known that the current price of this set of books is 12% lower than the original price. The original price of this set of books is______ Yuan

74.8 ^ (1-12%) = 74.8 ^ 0.88 = 85 yuan a: the price of this set of books is 85 yuan, so the answer is: 85

A and B leave from a and B with a starting speed of 3:2. When the two cars meet, a speeds up 15 and B speeds up 25. When a arrives at B, B still needs 26 kilometers to arrive at a, so as to find the distance between a and B

After meeting, a has to walk 33 + 2 = 25, the time required is 25 ^ [3 × (1 + 15)] = 25 ^ [3 × 65] = 19; so the distance between two points AB is 26 ^ [35 - (1 + 25) × 2 × 19] = 26 ^ [35-75 × 2 × 19], = 26 ^ [35-1445], = 26 ^ [1345, = 90 (km). A: the distance between two points AB is 90 km

For any a ∈ [- 2,2], the value of function f (x) = x ^ 2 + (A-4) x + 4-2a is always positive, and the value range of X is obtained

Consider the function f (x) as a function of A
f（x）=x^2+(a-4)x+4-2a
=（x-2）a+x^2-4x+4
For any a ∈ [- 2,2], constant greater than 0
That is, a = - 2 and 2 are always greater than 0
2 (X-2) + x ^ 2-4x + 4 is greater than 0
-2 (X-2) a + x ^ 2-4x + 4 is greater than 0
Simplify
X ^ 2-2x greater than 0
X ^ 2-6x + 8 greater than 0
Simplify
X (X-2) is greater than 0
(x-4) (X-2) is greater than 0
The solution is x greater than 4 or X less than 0
So the value range of X is greater than 4 or less than 0

The distance between a and B is 360 km. A bus and a truck leave from two places at the same time. After five hours, the two places meet. It is known that the speed ratio of the bus and the truck is 4:5, so what are the speeds of the bus and the truck!

Bus speed
360÷5×4/（4+5）
=72×4/9
=32 km / h
Truck 32 △ 4 × 5 = 40 km / h

A mathematical projective problem
If vector a = (2,3) and vector b = (- 4,7), what is the projective quantity of vector a on vector B? (there must be a problem-solving process)

The module of a multiplied by the included angle = a dot multiplied by B divided by the module of B = 65 under the root of 5

It was originally planned that 120 people would complete the construction of a section of highway in 50 days. After 30 days of work, 20 people were transferred to other sections to rush to repair. In this way, how many days will it take the remaining people to complete the task?

1 △ 120 × 50 = 16000 (1-16000 × 30 × 120) △ 16000 × (120 − 20)] = (1-35) △ 160 = 25 △ 160 = 24 (days) a: the rest of the people need 24 days to complete the task

From 1,2,3,4 , 20132014 these natural numbers, you can take a few numbers at most, so that the difference between each two numbers is not equal to 4!
Such as the title

Find the congruence set {1,5,9,13,..., 20092013} {2,6,10,14,..., 20102014} {3,7,11,15,..., 20072011} {4,8,12,16,..., 20082012} the elements in any two sets can't be 4, so if you have the most, just pick out the most from each set

The speed of a passenger train is 60 kilometers per hour, and that of a freight train is 45 kilometers per hour. The freight train is 105 meters longer than the passenger train. If the two cars are on the same level, the speed of a passenger train is 60 kilometers per hour, and that of a freight train is 45 kilometers per hour
The speed of a passenger car is 60 km / h, and that of a freight car is 45 km / h. The freight car is 105 meters longer than the passenger car. If two cars are running on parallel tracks and the passenger car catches up with the freight car from behind, the time they meet (i.e. from the moment when the front of the passenger car catches up with the rear of the freight car to the moment when the rear of the passenger car leaves the front of the freight car) is 1 minute 30 seconds
Question 1: find the respective lengths of the two cars
Q2: if two cars are going in opposite directions, what is the crossing time?

Take the freight car as the reference to determine the relative speed of the passenger car
① When catching up in the same direction, the relative speed of the bus is 60-45 = 15 km / h = 250 km / min;
The length of freight car = 250 × 1.5 = 375 km; the length of passenger car = 375-105 = 270375 km
② When traveling in opposite directions, the relative speed of the bus is 60 + 45 = 105 km / h = 1750 km / min;
Rendezvous time = 375 / 1750 = 3 / 14 minutes = 90 / 7 seconds

The current price of Andersen's fairy tales is 20 yuan, 1 / 6 lower than the original price. How much is the original price?