Answer:
30 mph
Step-by-step explanation:
Let d = distance (in miles)
Let t = time (in hours)
Let v = average speed driving <u>to</u> the airport (in mph)
⇒ v + 15 = average speed driving <u>from</u> the airport (in mph)
Using: distance = speed x time
![\implies t=\dfrac{d}{v}](https://tex.z-dn.net/?f=%5Cimplies%20t%3D%5Cdfrac%7Bd%7D%7Bv%7D)
Create two equations for the journey to and from the airport, given that the distance one way is 18 miles:
![\implies t=\dfrac{18}{v} \ \ \textsf{and} \ \ t=\dfrac{18}{v+15}](https://tex.z-dn.net/?f=%5Cimplies%20t%3D%5Cdfrac%7B18%7D%7Bv%7D%20%20%5C%20%5C%20%5Ctextsf%7Band%7D%20%5C%20%5C%20%20t%3D%5Cdfrac%7B18%7D%7Bv%2B15%7D)
We are told that the total driving time is 1 hour, so the sum of these expressions equals 1 hour:
![\implies \dfrac{18}{v} +\dfrac{18}{v+15}=1](https://tex.z-dn.net/?f=%5Cimplies%20%5Cdfrac%7B18%7D%7Bv%7D%20%2B%5Cdfrac%7B18%7D%7Bv%2B15%7D%3D1)
Now all we have to do is solve the equation for v:
![\implies \dfrac{18(v+15)}{v(v+15)} +\dfrac{18v}{v(v+15)}=1](https://tex.z-dn.net/?f=%5Cimplies%20%5Cdfrac%7B18%28v%2B15%29%7D%7Bv%28v%2B15%29%7D%20%2B%5Cdfrac%7B18v%7D%7Bv%28v%2B15%29%7D%3D1)
![\implies \dfrac{18(v+15)+18v}{v(v+15)}=1](https://tex.z-dn.net/?f=%5Cimplies%20%5Cdfrac%7B18%28v%2B15%29%2B18v%7D%7Bv%28v%2B15%29%7D%3D1)
![\implies 18(v+15)+18v=v(v+15)](https://tex.z-dn.net/?f=%5Cimplies%2018%28v%2B15%29%2B18v%3Dv%28v%2B15%29)
![\implies 18v+270+18v=v^2+15v](https://tex.z-dn.net/?f=%5Cimplies%2018v%2B270%2B18v%3Dv%5E2%2B15v)
![\implies v^2-21v-270=0](https://tex.z-dn.net/?f=%5Cimplies%20v%5E2-21v-270%3D0)
![\implies (v-30)(v+9)=0](https://tex.z-dn.net/?f=%5Cimplies%20%28v-30%29%28v%2B9%29%3D0)
![\implies v=30, v=-9](https://tex.z-dn.net/?f=%5Cimplies%20v%3D30%2C%20v%3D-9)
As v is positive, v = 30 only
So the average speed driving to the airport was 30 mph
(and the average speed driving from the airport was 45 mph)
15 you have to do all the steps thank it this I think
Answer:
I dont understand th equestion
Step-by-step explanation:
275 because 55 times 5 equals 275 ! Hope this helps