While you've been given the answer, I would like to cover the METHOD behind it. This way if prompted with a similar question you'll be able to figure it out for itself! While there are shorter ways, I'm going to logically reason this out so you can understand how to think about this problem.
To begin with, we know how many feet there are in a mile: 5,280 feet. Our vehicle under consideration travels 3/8 of that distance. While you can leave that in fractional form, I like to convert fractions to decimals, so 3/8 = 3 divided by 8 = 0.375. Now, to figure out the distance travelled we perform simple multiplication: 5,280 x .375, which equals 1,980 feet. So, our car travelled 1,980 feet in 13.946 seconds.
Now that we know that, we need to figure out how far the car moved per second, so we divide 1,980 (distance) by 13.946 (time) to get...a quite lengthy long-division problem. Since our original time was worked out to the thousands place, I'll work mine out similarly. So, working the problem out to 3 significant digits, I get 141.976 feet traveled per second.
It's easy from here
We know there are 60 seconds in minute and 60 minutes in an hour, so we need to do a little simple multiplication: 141.976 per second x 60 seconds tells us that our vehicle travels 8518.560 feet per minute. Multiplying 8518.560 feet per minute x 60 minutes tells us that the vehicle would travel 511113.600 feet in an hour. Okay, now we simply have to divide that number by our known constant: there are 5,280 feet in a mile. So, 511113.600 feet x 5,280 feet gives us a number of...96.802.
So what do we do with this number? Our answer tells us that if speed were to remain constant, our vehicle would travel 96.802 miles in one hour's time, so our vehicle is travelling at 96.802 Miles per hour (Mph).
Hopefully, this explanation is clear enough to understand HOW we all derived our answers, and will allow you to do so in the future!
P.S. Jives used some simple algebra to save himself quite a lot of time. If you know algebra, then it is a simple matter. If you need to know where Jives got 3600 seconds from, that is simply how many seconds there are in an hour.
