A mathematical problem requires a formula Among the 319 cities monitored in 2006, 37.3% of them have air quality of grade III. how many cities have air quality of grade III?

A mathematical problem requires a formula Among the 319 cities monitored in 2006, 37.3% of them have air quality of grade III. how many cities have air quality of grade III?

The number of cities with air quality level 3 = the total number of cities × the percentage of cities with air quality level 3 in the total number of cities
If I insist on the formula, I can only write it like this=
Using image method to solve binary linear equations: 5x = y + 43x + 2Y − 18 = 0
As shown in the figure: it can be seen from the figure that the line y = 5x-4 and y = - 1.5x + 9 intersect at the point (2,6), so the solution of the binary linear equation system: 5x = y + 43x + 2Y − 18 = 0. Is x = 2Y = 6
The results show that: 1) 4x + 3 × 0.7 = 6.5; 2) x: 8 = 34:115; 3) 2x + 2 × 0.7 = 4.5; 4) x: 8 = 14:15
①4x+3×0.7=6.5，     4x+2.1-2.1=6.5-2.1，             4x=4.4，          4x÷4=4.4÷4，              x=1.1；②x：8=34：115，      115x=8×34，115x÷115=6÷115，       x=5；③2x+2×0.7=4.5， 2x+1.4-1.4=4.5-1.4，         2x=3.1，      2x÷2=3.1÷2，          x=1.55；④x：8=14：15，    15x=8×14，15x÷15＝2÷15，     x=10．
A mathematical problem should have process and calculation formula
A conference hall has six cylindrical wooden columns of the same size, each of which is 5 meters high and the perimeter of the bottom surface is 1.2 meters?
That is to find the side area of the cylinder
The perimeter of the bottom surface is 1.2 meters
So the side area = the perimeter of the bottom multiplied by the height
There are six
So the side area is (1.2 * 5) * 6 square meters
So (1.2 * 5) * 6 △ 4.5 = 6 * 6 △ 4.5 = 36 △ 4.5 = 8kg
Solve the equations 5x + 2Y = 253x-4y = 15
5x + 2Y = 25, 1 3x-4y = 15, 2, 2 + 1 × 2 get: 13X = 65, x = 5, substituting x = 5 into 1 get: 25 + 2Y = 25, y = 0, the solution of the equations is x = 5Y = 0
The solution of the equation 3x + 4x = 6 is
3x+4x=6
7x=6
X = 6 / 7
Is LZ wrong
Should be
3x+4y=6
x=2 y=0
Is the title wrong? Maybe 3x + 4Y = 6
No natural number solution
unsolvable
From the meaning of the title: 7x = 6, x = 7 / 6
Because 7 / 6 is not a natural number,
It's against the theme
So x has no natural number solution
7x=6
x=6/7
Give formula
The circumference of the circle is 2080 mm
Please try not to use English letters because I can't understand them
Circumference of circle = 3.14 times diameter
2080 = 3.14 times diameter
Diameter d = 662mm
Perimeter = 2 times π times radius
Circumference = π times diameter
Perimeter = diameter times π
Diameter = 2080 / π
Π = diameter times perimeter
Diameter = perimeter divided by Π
That is diameter = 2080 / Π = 2080 / 3.14 ≈ 662.4 (mm)
Perimeter = Πtimes diameter
Diameter = perimeter divided by Π
That is diameter = 2080 / Π = 2080 / 3.14 ≈ 662.4 (mm)
Reduction: (1) x ^ 2 + 2x + 1 / x ^ 2 + X; (2) 3x-6 / x ^ 2-4x + 4; (3) ax ^ 2 / A + ax
Wrong type, should be: (1) (x ^ 2 + 2x + 1) / (x ^ 2 + x); (2) (3x-6) / (x ^ 2-4x + 4); (3) (AX ^ 2) / (a + ax)
（1）（x+1）^2/{x(x=1)}=(x+1)/x
(2) 3(x-2)/(x-2)^2=3/(x+2)
(3) a(x)^2/a(1+x)=x^2/(1+x)
It is known that the equation 3x-6 (x-a / 2) = 4x and 3x + A / 12-1-5x / 8 = 1 have the same solution. Find the value of a and the solution of the equation
From the first formula, we can get: 3A = 7x, so a = 3 / 7X
From the second formula, 2A + 57x = 48
Substituting a = 3 / 7X into the second simplified formula lesson, we can get a and X
Proof of logarithm exchange formula
loga^b=loga/logb?
N
Let y = loga
Y
Then a = n
Take the logarithm of a as the base on both sides
A N
ylogm ＝logm
N
logm
y＝－－－－－
A
logm
N
N logm
That is, loga = - -
a ．
logm
Let a ^ B = n (1)
Then B = Logan II.
The logarithm identity is obtained by substituting (2) into (1)
a^(logaN)=N………… 3.
Take the logarithm of m as the base on both sides of 3
logaN·logma=logmN
therefore
logaN=(logmN)/(logma)