Jill drove the 200 miles to Cincinnati at an average speed of 10 miles per hour faster than her usual average speed. If she completed the trip in 1 hour less than usual, what is her usual driving speed, in miles per hour

Let be the usual speed, and be the usual time.

Following the equation , where s is the space, v is the velocity and t is time, we know that usually we have

But this time we were 10mph faster and it took one hour less, so we have

Since both right hand sides equal 200, they must equal each other:

Plug this value in the first equation and we have

This equation has solutions . We can only accept positive solutions, so we have t=5. We finally deduce, again from the first equation,

answer is  

a.

93.98 sq. in.

hope you got it chief