Math:Brain Buster!!!

K.Snyder · Post by **K.Snyder** » Wed Apr 13, 2005 5:06 am

Well I know this may sound stupid but i am having trouble trying to figure out the average speed of a vehicle that travels 3/8 of a mile in 13.946 second in Mph. For all you Math wizards out there its probably simple for you!!!Thx :-3

K.Snyder

Philadelphia Eagle · Post by **Philadelphia Eagle** » Wed Apr 13, 2005 7:05 am

How about 96.80 mph?

lady cop · Post by **lady cop** » Wed Apr 13, 2005 7:09 am

Philly, i KNEW you'd be the one!

devist8me · Post by **devist8me** » Wed Apr 13, 2005 7:20 am

Philadelphia Eagle wrote: How about 96.80 mph?

Good Job! Not that I can check your answer

but I'd say your pretty sure if you posted it.

Jives · Post by **Jives** » Wed Apr 13, 2005 7:31 am

Set it up as a proportion:

13.946 sec is to 3600 sec as 0.375 mi. is to X mi.

cross multiply and divide.

I got 96.80195 MPH

chonsigirl · Post by **chonsigirl** » Wed Apr 13, 2005 7:33 am

Wow, same subject as the math lesson in my class for the day-I should try your example.

minks · Post by **minks** » Wed Apr 13, 2005 8:10 am

MATH!

Isn't that a swear word??????

hotsauce · Post by **hotsauce** » Wed Apr 13, 2005 8:12 am

we have some smarties in here!

i liked language arts...had nighmares about math!

minks · Post by **minks** » Wed Apr 13, 2005 8:24 am

me to Hot I took math 10 4 times in high school, now that is bad.

I am supposed to be helping a woman with basic math this year as part of my literacy training work and I really don't know why they matched us like that. I have to learn the dam basics over in order to teach them not sure how this is going to work ahahaha

pink princess · Post by **pink princess** » Wed Apr 13, 2005 8:38 am

minks wrote: MATH!

Isn't that a swear word??????
fantastic! :wah:

Hawke · Post by **Hawke** » Wed Apr 13, 2005 9:30 am

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.

K.Snyder · Post by **K.Snyder** » Wed Apr 13, 2005 7:43 pm

Thx guys.I appreciate your help.