How to do the fourth question?

How many times in the 24 hours of the day do the hour, minute and second hands of the clock coincide exactly?

11 2 = 22 times.

1 o'clock, 13:30 (another 5 11 minutes.)

2 o'clock, 2 p.m. 60 p.m. (10 11 p.m.)

3 o'clock, 15:90 (4 11 minutes.)

4 o'clock, 16 o'clock 120 (again 9 11 minutes.)

5 o'clock, 17 o'clock 150 (again 3 11 minutes.)

6 o'clock, 18 o'clock 180 (again 8 11 minutes.)

7 o'clock, 7 p.m. 210 (again 2 11 minutes.)

8 o'clock, 20 o'clock 240 (again 7 11 minutes.)

9 o'clock, 21 o'clock 270 (again 1 11 minutes.

10 o'clock, 22 o'clock 300 (again 6 11 minutes.)

12 o'clock and 24 o'clock.

Tiananmen Square covers an area of x million square meters.

Then there are 2x-16 72

x 44, so Tiananmen Square covers an area of 440,000 square meters.

If the chair is x, the stool is 18 minus x

This is a typical chicken-rabbit problem in the same cage, and if you don't learn to set the unknowns, you can do it one by one, and if the stool is one, then see if it's correct.

Suppose the stool is two.

First of all, take an object of the exact same shape, put it upside down on the object, then it becomes a cylinder with a height of 3+.

Whereas, the required volume of the object is half the volume of the cylinder.

3 2) 丌x(3+cm³.)

You can first calculate the height of the volume of a cylinder with a diameter of 3cm, and half of the volume of this cylinder plus the volume of the cylinder with a height of 3cm and a diameter of 3cm is the volume of the object on the **.

h=, bring in the formula. The diameter is not clear.

Solution: Four.

The number on the train above is J.K

The numbers below the train above are:

The number above the train below is the state of hand:

The number below the train below is:

Fill in the numbers in order, two rows of numbers for each vehicle, in forward or reverse order.

It shows that f(x) exists at the limit at x=1, and the limit value is the function value, when x 1, (x +bx+2) (1-x), the denominator = 0, for the limit to exist, then the numerator = 1 + b + 2 = 0, b = -3

At this point the molecule = x -3x + 2 = (x-1) (x-2), then (x + bx+2) (1-x) = 2-x, so lim(x 1) f(x) = 2-1 = 1

f(1)=a=lim(x→1)f(x)=1

lim(x tends to 1)(x 2+bx+2) (1-x)=a, the denominator tends to 0, there is a limit.

So the molecule tends to 0

All x=11+b+2=0

So lim(x tends to 1)(x-1)(x-2) (1-x)=alim(x tends to 1)(2-x)=a

So a=2-1

So a=1b=-3

In the fourth round of the Chinese Super League, Tianjin Quanjian 0-11 Guangzhou Evergrande**.

Na: Total = (40 + 50) 3 4 = 1080

1080 3 4 = 810 left

Also needed: 810 40 = 21 days (here it is a whole number).