In the sixth grade, girls accounted for 1 / 3 of the total. Later, six girls were transferred in. In this way, girls accounted for 4 / 9 of the total?

In the sixth grade, girls accounted for 1 / 3 of the total. Later, six girls were transferred in. In this way, girls accounted for 4 / 9 of the total?

There were X students,
(1/3 X+6)/(X+6)=4/9
(1/3 X+6)*9=(X+6)*4
3X+54=4X+24
X=30

The sixth grade students of a school participate in the calligraphy competition and are divided into two groups. The number ratio of group A and group B is 5:6,
The number of people in group A is 5 / 4 of the number of people in group A. There are () people participating in the calligraphy competition

If there are 5 x people in group A, there are 6 x people in group B
5x=5/4(6x-8)
If you multiply both sides of the equation by four, you get four
20x=5(6x-8)
20x=30x-40
10x=40
x=4
5x=20 6x=24
5x+6x=20+24=44

1-2^(-2008)/1-2^(-1)
Simplification

The denominator is 1-1 / 2 = 1 / 2
So the original formula = 2 (1-2 ^ (- 2008)) = 2-2 ^ (- 2007)

Solution inequality: 9-x2 ≤ 0 solution is 2x2-3x-2 > 0 solution is - 3x2 + 5x ≥ 2 solution is - x2 + 2x-1 > 0 solution is - x2 + 2x-3 ≤ 0 solution is urgent

9-x2≤0
x2-9>=0
(x+3)(x-3)>=0
The solution is: x > = 3; x0
(2x+1)(x-2)>0
The solution is: x > 2; x > 2

The perimeter of a circle is equal to that of a square, which is 314cm. How much larger is the area of a circle than that of a square?

The circumference of circle C = 2 π R, r = C / 2 π = 50cm, circle area s = π R × r = 7850, square circumference C = 4A, side length a = C / 4 = 78.5cm, square area s = a × a = 6162.25, circle area is 7850-6162.25 larger than square area = 1687.75

Of the following numbers, the number greater than 13 and less than 12 is ()
A. 512B. 413C. 712D. 612

Because 12 = 1 × 62 × 6 = 612, 13 = 1 × 43 × 4 = 412, then 712 ＞ 612 ＞ 512 ＞ 412, so 512 is between 13 and 12; and because 612 ＞ 412 ＞ 413, among the four options, only 512 is greater than 13 and less than 12

32 plus 16 plus 8 plus 4 plus 2 plus 1 minus 1 / 2 minus 1 / 4 minus 1 / 8 minus 1 / 16 minus 1 / 32

32 plus 16 plus 8 plus 4 plus 2 plus 1 minus 1 / 2 minus 1 / 4 minus 1 / 8 minus 1 / 16 minus 1 / 32
=[32+16+8+4+2+1+1]-1-[1/2+1/4+1/8+1/16+1/32+1/32]+1/32
＝64-1-1+1/32＝1985/32

The calculation formula of arc length of bow is known that the chord length is 7.4M and the height is 1.2m

Let the radius of the sector be r, the height of 1.2m be a part of the end of the radius r, the remaining part be (R - 1.2), and the half length of the chord be 3.7m, then (R - 1.2), 3.7 and R form an oblique

Summation formula of arithmetic sequence (the one without tolerance)

Sn = (a1 + an) n / 2 Sn = A1N + n (n-1) d / 2 D = tolerance Sn = an2 + BN, a = D / 2, B = A1 - (D / 2)

4 out of 7 and 3 out of 8 of a certain number are 1.5 times of 3.16. To find a certain number (the solution of a series of equations)

Let this number be X
4 / 7 × 3 / 8 × x = 3.16 × 1.5
3x of 14 = 4.74
X = 4.74 △ 3 / 14
x=22.12