16: 20 = 32: () = () 5 / 5 () = (): 0.2

16: 20 = 32: () = () 5 / 5 () = (): 0.2

16: 20 = 32: () = () 5 / 5 () = (): 0.2
16：20=32：（）
()=32/16*20=40
16：20=（）÷(（）/5)
()/()=16/(20*5)=16:100
16：20=（）：0.2
()=16*0.2/20=0.16
So:
16: 20 = 32: (40) = (16) × 5 / 5 (100) = (0.16): 0.2

4: 3, 12:9, (), 108:81 and 10:2 = 20:4, 20:4 = 40:8, (), 80:16 = 160:32

1. If the first and second terms are multiplied by 3 at the same time, then 36:27
2. Because the product of internal terms is equal to the product of external terms, it can be calculated

Rule finding by oral calculation

Number of the first column: 8 4 16 8 32 16 [64] [32]
The rule is: every other observation, the latter is twice the former
8×2=16
16×2=32
32×2=64
4×2=8
8×2=16
16×2=32
Number of the second column: 100 10 90 20 80 30 [70] [40]
The rule is to observe every other time
10、20、30、（40）

In the arithmetic sequence, there are 2n + 1 terms. How to prove that (s odd) divided by (s even) equals n divided by (n-1)?

Let the first term be a and the tolerance be d
Then the first term is a, the second term is a + D, the last term is a + 2nd, and the last penultimate term is a + (2n-1) d
Odd number has n + 1 term, even number has n term
The odd term forms the arithmetic sequence with the first term of a, the last term of a + 2nd and the tolerance of 2D
Even number terms form the arithmetic sequence with a + D as the first term, a + (2n-1) d as the last term and 2D as the tolerance
S odd = (a + A + 2nd) * (n + 1) / 2 = (a + nd) (n + 1)
S-even = [a + D + A + (2n-1) D] * n / 2 = (a + nd) * n
S odd / s even = (n + 1) / n
It is different from the conclusion to be proved
To prove that the title is wrong, give an example
Let 1 2 3 4 5
Then 2n + 1 = 5, n = 2
S odd = 1 + 3 + 5 = 9
S even = 2 + 4 = 6
S odd / s even = 9 / 6 = 3 / 2
N / (n-1) = 2 / 1 = 2 ≠ s odd / s even
(n + 1) / N = (2 + 1) / 2 = 3 / 2 = s odd / s even
Obviously the title is wrong

If the first number is multiplied by 2, the second number remains unchanged, and the third number is divided by 2, the three numbers obtained will still be an arithmetic sequence
Find these three numbers?

Let three numbers be a, B and C respectively
1）a+b+c=18
2）a-b=b-c
3) 2a-b = B-C / 2 solve this system of linear equations with three variables and get: a = 4, B = 6, C = 8

8 / 8 = 32 / 8 = () divided by 4 = 80 divided by () = 0.5

4 out of 8 = 32 out of 64 = (2) divided by 4 = 80 divided by (160) = 0.5

2 / 9 divided by [(1 / 2 + 1 / 6) * 3 / 4]

4/9

[7th - (- 3rd) - (+ 5th)] divided by (- 105th) velocity,

[1 / 7 - (- 1 / 3) - (+ 1 / 5)] divided by (- 1 / 105)
= [1 / 7 + 1 / 3-1 / 5] × (- 105)
= 1 in 7 × (- 105) + 1 in 3 × (- 105) - 1 in 5 × (- 105)
＝－15＋（－35）＋21
＝－50＋21
＝－29

How to dilute a liquid with multiple of 1:10, 1:20, 1:40, 1:80, 1:160, 1:320, 1:640 and 1:1280?
Is this method double dilution or tenfold dilution or double dilution?
Hope to get the specific operation steps and instructions, do not copy and paste over Oh!
It's mainly to help me solve the part of drawing the red line. How can I make these dilutions more easily?

The first one is 1:10 and 10 times, take 1L and 9L water, the second one is 1:20, which is twice of 1:10, take 10l10 times liquid 5L, add 5L water, that is 20 times, then take 20 times liquid 5L, add 5L water, that is 40 times, and so on

Simple calculation of 1 / 5-1 / 10-1 / 20-1 / 40-1 / 80-1 / 160

32/160 - 16/160 - 8/160 - 4/160 - 2/160 - 1/160 =1/160
Change the denominator to 160, and the molecules change at the same time
It seems that this is not a simple calculation. There should be a simpler way. I can't think of it. I haven't used my brain for many years
What grade is this? It's so difficult ha-ha