Answer:
75000 Hz
Explanation:
f = V / λ (f= frequency, v=velocity of wave, lambda= wavelength)
alternatively, f = c / λ (f= frequency, c= speed of light- 3.00x10^8 m/s, lambda= wavelength)
f= [3.00x10^8 m/s]/[4000 m]
=75000 Hz
Answer: A dilation with rule: 
Explanation:
A dilation is a non-rigid transformation that creates an image that is the same shape as the original but has a different size.
It uses a scale factor k such that

(x,y)= coordinates of original figure
(kx,ky) = corresponding coordinate in the image.
To transform: A (3,-4) onto point A' (1.5,-2).
Using scale factor k=
, we have

Required rule: 
Explanation:
1 literThe total of water is equal to 1000.0 g of water
we need to find the molality of a solution containing 10.0 g of dissolved in Na₂S0₄1000.0 g of water
1. For that find the molar mass
Na: 2 x 22.99= 45.98
S: 32.07
O: 4 x 16= 64
The total molar mass is 142.05
We have to find the number of moles, y
To find the number of moles divide 10.0g by 142.05 g/mol.
So the number of moles is 0.0704 moles.
For the molarity, you need the number of moles divided by the volume. So, 0.0704 mol/1 L.
The molarity would end up being 0.0704 M
The molality of a solution containing 10.0 g of Na2SO4 dissolved in 1000.0 g of water is 0.0704 Mliter