Find the nth number of the rule

Find the nth number of the rule

-2N+1

Study the following series of numbers: 1, - 3, 5, - 7, 9, - 11, 13 According to this rule, the nth number should be ()
A. 2n-1B. 1-2nC. （2n-1）（-1）nD. （2n-1）（-1）n+1

The nth number is (2n-1) (- 1) n + 1

Write the nth number according to the rule

2N-1

How to calculate the area of a pool?

Measure the depth of the pool, divide the volume by the depth, and that's the area

How much does a 50 cubic meter pool cost

How big is your pool? At least explain it first. I can't talk to you here

For a water storage tank, after 70 / 100 water storage is used, 100m cubic meters is added. This is half of the original water. How many cubic meters of the original water?
There must be a formula!

Original water x M3
(1-0.7)x + 100 = 0.5x
X = 500 (M3)

A farm is going to build a cuboid tank with a volume of 100m, and the bottom of the tank is square
(1) Write out the functional relationship between the depth of the reservoir y and the length of the bottom edge X. (2) if the depth of the reservoir is set at 4m, how many meters is the length of the bottom edge of the reservoir?

x*x*y=100
x*x*4=100
x=5

If the small pool is filled with water, there will be 5 tons of water left in the small pool; if the small pool is filled with water, there will be 30 tons of water left in the large pool. It is known that the capacity of the large pool is 1.5 times that of the small pool. How many tons of water are left in each of the two pools
How many tons are the two pools in total

There are x tons of water in small pool and 1.5x tons in large pool
1.5x+5=x+30
x=50
∴1.5x=45
There are 95 tons of water

There are two pools a and B with a total water storage capacity of 40 cubic meters. If pool a is injecting 4 cubic meters of water and Pool B is discharging 8 cubic meters of water, then the water injection volume of pool a and B is equal. How many cubic meters of water are the two pools injected?

Set up a pool with original water injection of X cubic meters
X+4=（40-X）-8
[(x + 4) is 4m3 of water injected into pool a, (40-x) is the original number of water injected into pool B, (40-x) - 8 is 8m3 of water discharged from pool b]
I don't know if you can understand this explanation

The diameter of a circular pool is 40 meters. Draw it on a drawing with a scale of 1:1000. How many centimeters is the circumference of the circular pool on the drawing?

1:1000=x:40
x=0.04m=4cm
The circumference of the round pool is 4 * 3.14 = 12.56 cm