2/30 cause you can simplify easy
239.99 x 75%(75/100) ~ $180
$180 x 90%(90/100) = $162
Answer:
The intensity becomes one fourth when the distance is doubled.
Step-by-step explanation:
The statement is
Intensity of light
varies inversly as the square of the distance ![d](https://tex.z-dn.net/?f=d)
So we get
![l=\frac{k}{d^2}](https://tex.z-dn.net/?f=l%3D%5Cfrac%7Bk%7D%7Bd%5E2%7D)
Now for distance 12in let the intensity be ![l_{1}](https://tex.z-dn.net/?f=l_%7B1%7D)
So we get
![l_{1}=\frac{k}{12^2}](https://tex.z-dn.net/?f=l_%7B1%7D%3D%5Cfrac%7Bk%7D%7B12%5E2%7D)
...(1)
For distance 24in, let the intensity be ![l_{2}](https://tex.z-dn.net/?f=l_%7B2%7D)
We get
![l_{2}=\frac{k}{24^2}](https://tex.z-dn.net/?f=l_%7B2%7D%3D%5Cfrac%7Bk%7D%7B24%5E2%7D)
....(2)
Dividing (1) by (2) we get
![\frac{l_{1}}{l_{2}}=\frac{ \frac{k}{144}}{ \frac{k}{576}}=\frac{576}{144}](https://tex.z-dn.net/?f=%5Cfrac%7Bl_%7B1%7D%7D%7Bl_%7B2%7D%7D%3D%5Cfrac%7B%20%5Cfrac%7Bk%7D%7B144%7D%7D%7B%20%5Cfrac%7Bk%7D%7B576%7D%7D%3D%5Cfrac%7B576%7D%7B144%7D)
![\frac{l_{1}}{l_{2}}=4](https://tex.z-dn.net/?f=%5Cfrac%7Bl_%7B1%7D%7D%7Bl_%7B2%7D%7D%3D4)
![l_{1}=4l_{2} \ or \ l_{2} = \frac{1}{4}l_{1}](https://tex.z-dn.net/?f=l_%7B1%7D%3D4l_%7B2%7D%20%5C%20or%20%5C%20l_%7B2%7D%20%3D%20%5Cfrac%7B1%7D%7B4%7Dl_%7B1%7D)
Hence the intensity becomes one fourth
Let x be the speed when Fritz is driving
x + 6 will be the train speed
Converting minutes to hrs
48 mins = 48/60 = 4/5 hrs
40 mins = 40/60 = 2/3 hrs
Remember formula distance = rate * time
distance driving = (4/5)x
distance train traveling = (2/3)(x+6)
The train travels the same distance as the car
4/5x = 2/3(x+6)
4/5x = 2/3x + 4
4/5x - 2/3x = 4
basic elementary school math
2/15x = 4
2x = 40
x = 30 miles/hrs is the speed he driving.
distance train traveling = 2/3(30 + 6) = 24 miles
check with the distance he driving
4/5(30) = 24 miles