Speed Question

Re: Speed Question


Let the distance in miles between towns A and B be D.
The car travels at a speed of D/5 miles/hr.
The van travels at a speed of D/7 miles/hr.
The van left 2 hours after the car.

Let t represent the time elapsed since 10:00 AM when the car set out.

At the time, t, at which they pass, the car has travelled tD/5 miles and the van has travelled (t-2)D/7 miles.

In order for the vehicles to pass, tD/5 + (t-2)D/7 must equal the total distace, D.

tD/5 + (t-2)D/7 = D

t/5 +(t-2)/7 = 1

t/5 + t/7 -2/7 = 1

12t/35 = 1 + 2/7
12t = 35 + 10 = 45
t = 45/12 = 3 3/4
Since t was defined as the time elapsed since 10 AM, the vehicles will pass at 1:45 PM.

ok
Thank you for your help.

The question has a hole in it though. It could be anytime between 3 and 5 I believe, but I have a horrible headache and haven't had much sleep so I could be horribly mistaken.

Edit: yup, it's confirmed on a decent amount of sleep that this post makes no sense. disregard it.

yes
Yes, the answer is 1:45pm. Good job.

fdrhs, this is carlotta replying to a question you posed in one of the writing forums.

If you are looking for a way to propose a Math book to a publisher, I may have some advice that could help you. I sensed from your question, "What are the steps to write a book?" and the follow up, "I want to write a Math book for children" that you are an educator not a writer per se. Not that you can't be both!

If you are looking for practical help in writing a proposal, I am at your service. If you are looking for a math whiz, uh oh, I'm the last person you can count on.

ok
Carlotta,

I don't want to be a writer per se. However, I got very good grades in all my writing courses. I just have been anxious to write an easy book for kids to learn math.

fdrs -

I am so glad that you want to do that. People who have special talents, such as yours in Math, are the ones we count on to share that knowledge.
What age group do you want to reach?
Are you considering a text book? A work book? A concept book?
If you are planing an educational style book with activities, may I suggest a trip to your nearest Barnes and Noble. Go to the educational section and look for the books that are closest to what you have in mind. Study them, looking particularly for the way the content is layed out, and how many pages. Books (all) have set numbers of pages based on multiples of 8. A traditional picture book has 32 pages. A traditional work/activity book has a minimum of 64 pagaes. Most have 96.
Content, style of presentation, and page number are the first things to decide.

If you have a picture book in mind, let me know.

best to you,
carlotta

ok
Carlotta,

Thank you for the positive feedback. My goal is to one day write math high school math books without the complicated terminology that scares most students. I want to create "Baby-Talk" Math books for high school students.