8 seconds
The hardest part of this is setting up the equation -- the calculations are pretty easy.
You're told that the time (needed to go from 0 to 100 MPH) is inversely proportional to the horsepower: what this means is that as horsepower gets larger, time gets smaller. This makes sense since the more horsepower you have, the less time it will take you to get to 100 MPH
You can think of this as:
200 HP = 10 seconds
250 HP = x seconds
You set the equation up as:
250 HP / 200 HP = 10 sec / x sec
Now, just cross multiply and solve:
250 / 200 = 10 / x
250x = (200 x 10)
250x = 2000
x = 2000 / 250
x = 8
So, as you increase the horsepower from 200 to 250, the time decreases from 10 seconds to 8 seconds.
Hope this helps!
Good luck.
This is the answer for both number 9 and number 11.
Good luck
3/5 = .6 and 4/10 = .4, so 3/5 is greater than 4/10
Subtract 8 from both sides
So you end up with x = -23
