I believe the answer would be 164 <span />
Answer:
687.5
Step-by-step explanation:
To find the equivalent expression, simplify the operations using order of operations.
2.50(600 - 500*.25) - 500 Multiply -500*0.25
2.50(600 - 125) - 500 Subtract 600 - 125
2.50(475) - 500 Multiply 2.50(475)
1187.5 - 500 Subtract
687.5
Answer: $255.58
Step-by-step explanation:
$310.30*0.07= $21.721
$310.30-$21.72= $255.579
<u>Round</u>
$255.579 --> $255.58
Answer:
The distance between the ghost changes at 10 pm approximately at a rate of 24.981 kilometers per hour.
Step-by-step explanation:
At first we assume that north and east directions both represent positive quantities. Let suppose that
and
. If both ghosts moves at constant velocity such that
and
, then the final positions of both ghosts are, respectively:
Ghost A
(Eq. 1)
Ghost B
(Eq. 2)
Where
is the time, measured in hours.
Then, the equations of motion of each ghost are, respectively:
Ghost A

![\vec r_{A} = \left(-15\cdot t, 0)\,\,\,\left[km \right]](https://tex.z-dn.net/?f=%5Cvec%20r_%7BA%7D%20%3D%20%5Cleft%28-15%5Ccdot%20t%2C%200%29%5C%2C%5C%2C%5C%2C%5Cleft%5Bkm%20%5Cright%5D)
Ghost B

![\vec r_{B} = (5, 20\cdot t)\,\,\,\left[km\right]](https://tex.z-dn.net/?f=%5Cvec%20r_%7BB%7D%20%3D%20%285%2C%2020%5Ccdot%20t%29%5C%2C%5C%2C%5C%2C%5Cleft%5Bkm%5Cright%5D)
Then, the distance between both ghosts is:
![\vec r_{B/A} = (5,20\cdot t)-(-15\cdot t, 0)\,\,\,[km]](https://tex.z-dn.net/?f=%5Cvec%20r_%7BB%2FA%7D%20%3D%20%285%2C20%5Ccdot%20t%29-%28-15%5Ccdot%20t%2C%200%29%5C%2C%5C%2C%5C%2C%5Bkm%5D)
(Eq. 3)
The magnitude of the relative is represented by the following Pythagorean identity:

Then, we find the rate of change of the relative distance (
), measured in kilometers per hour, by implicit differentiation:



(Eq. 4)
If we know that
, then the rate of change of the relative distance at 10 PM is:
![\dot r_{B/A} = \frac{75+625\cdot (4)}{\sqrt{[5+15\cdot (4)]^{2}+[20\cdot (4)]^{2}}}](https://tex.z-dn.net/?f=%5Cdot%20r_%7BB%2FA%7D%20%3D%20%5Cfrac%7B75%2B625%5Ccdot%20%284%29%7D%7B%5Csqrt%7B%5B5%2B15%5Ccdot%20%284%29%5D%5E%7B2%7D%2B%5B20%5Ccdot%20%284%29%5D%5E%7B2%7D%7D%7D)

The distance between the ghost changes at 10 pm approximately at a rate of 24.981 kilometers per hour.