Math Is Fun Forum

Denominator

Member

Registered: 2009-11-23

Posts: 220

Re: Stuck on previous exam questions!

Yes, I understand this now

Thank you bob and bobby and anonim!

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bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Stuck on previous exam questions!

Hi Denominator;

Your welcome!

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Stuck on previous exam questions!

You are very welcome.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

Re: Stuck on previous exam questions!

hi Denominator

Let the distance from Southampton to London be D, and the distance to the overtaking point be d.

Let the time in minutes from 9.17 to the overtaking point be t

The goods train takes 165 minutes
The express train takes 100 minutes

So the gradient (velocity in miles / min) for the goods train is

and for the express train

You can eliminate both D and d by dividing these equations:

and then solve for t.

Bob

How did you get that 39? Sorry, couldn't comprehend.

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Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.
May his adventurous soul rest in peace at heaven.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Stuck on previous exam questions!

hi Monox D. I-Fly

The express train starts off later.  See post #18.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Monox D. I-Fly

Member

From: Indonesia

Registered: 2015-12-02

Posts: 2,000

Re: Stuck on previous exam questions!

Oh, I see. The difference between 09.56 and 09.17, right? Took me some minutes to figure it out.

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Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.
May his adventurous soul rest in peace at heaven.