On the map with a scale of 1:3000000, it is measured that the distance between a and B is 3.6cm. How many hours can a car arrive from a tunnel B at a speed of 60km per hour?

3.6 △ 13000000, = 3.6 × 3000000, = 10800000 (CM), 10800000 cm = 108km, 108 △ 60 = 1.8 (H); a: it can be reached in 1.8 hours

The maximum and minimum values of the function y = 1-2cos π / 2x are

y=1-2cosπ/2x
-1≤cosπ/2x≤1
-2≤-2cosπ/2x≤2
-1≤1-2cosπ/2x≤3
Minimum - 1, maximum 3
Range [- 1,3]

The difference between a and B is 30, where 310 of a is equal to 13 of B, then the sum of the two numbers is______ ．

Let a be x, then B be 910x, & nbsp; & nbsp; x-910x = 30, & nbsp; & nbsp; & nbsp; 110x = 30110x △ 110 = 30 △ 110, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 300300 × 910 = 270300 + 270 = 570. A: the sum of these two numbers is 570, so we should fill in 570

Several proofs of Mean Value Inequality Chain in senior high school mathematics compulsory 5 inequality

Inequality is one of the core test points of high school mathematics, in which the basic inequality and the mean inequality chain play an important role in the process of solving problems. Combined with the tips in the textbook, this paper sums up several methods to prove the mean inequality chain, Note: arithmetic mean ---; geometric mean ---; harmonic mean ---; square mean ---
Proof 1: (algebraic method) proof 2: (geometric method) proof 3: (geometric method)

A and B set out from two places at the same time, and after four hours, they met at a distance of 4km from the midpoint. B was slower than a, and how many kilometers did a travel more than B per hour?
It is required to use the equation learned in grade five to solve the problem

Draw a line diagram and have a look
When we met, a had more lines than B: 4 × 2 = 8 km
Every hour, a has more lines than B: 8 △ 4 = 2km
Let a travel x kilometers more than B per hour
4x=4+4
4x=8
x=2
A: a travels 2 kilometers more per hour than B

The inequality of 1 solution about X
The solution set of x square + (K + 3) x + 3k0 is the range of R for a

1、（x+3）(x+k)3 -k

The passenger and freight cars leave the two cities 500 kilometers apart at the same time. After 2.5 hours, they meet on the way. The passenger cars travel 120 kilometers per hour, and the freight cars run 120 kilometers per hour
The passenger and freight cars leave the two cities 500 kilometers apart at the same time. After 2.5 hours, they meet on the way. The passenger car travels 120 kilometers per hour, and the freight car travels x kilometers per hour
＝500

Set up freight cars to travel x kilometers per hour
2.5*（X+120）=500
X = 80 km / h

Given vector a = (3,2), find the coordinates of the unit vector parallel to vector a, and find the coordinates of the unit vector perpendicular to vector a

To find the unit vector parallel to a vector, we only need to divide the vector by its module, and then add the sign before it. Because the module of a vector | a | = √ (3 + 2) = √ 13, the coordinate of the unit vector parallel to a is ± (3,2) / √ 13. There are two possibilities: (3 / √ 13,2 / √ 13), (- 3 / √ 13, - 2 / √ 13)

There are two workshops a and B in a factory. The number of workshop a accounts for 9 / 5 of the total number of the two workshops. After 70 people are transferred out of workshop a, the ratio of workshop a and B is 3:8. How many people are there
There should be a calculation process

The number of people in workshop B remains unchanged, set as unit "1"
Originally, workshop a was 5 / 4 of workshop B, and later it was 3 / 8,
Therefore, the number of people in workshop B is 70 (5 / 4-3 / 8) = 80
The original number of workers in workshop a is 80 × 5 / 4 = 100
Suggestion: please write 5 / 9 for 5 / 9

Among the natural numbers smaller than 1000, how many are there without 1?

If it is smaller than 1000, then assume that the number is ABC, a is a hundred, B is ten, and C is a single. ABC can fill in 0 and 9 except 1, so there are 9 * 9 * 9 = 729 numbers without 1

On the map with a scale of 1:3000000, it is measured that the distance between a and B is 3.6cm. How many hours can a car arrive from a tunnel B at a speed of 60km per hour?