Math Is Fun Forum

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Zomg Mass Pronumerals

A train that travels a km in b hours is p times as fast as a bus. If the bus takes m hours to cover the distance between two places, how many kilometres apart are the two places?
Answer: am/bp km

Uh I got this equation:

It doesn't really fit, but I don't see how it's wrong. ?_?

Dross

Member

Registered: 2006-08-24

Posts: 325

Re: Zomg Mass Pronumerals

1) The speed of the train is

. Since this is

(

being the speed of the bus), then:

(This much is pretty obvious, though...)

2) Since distance = speed x time, (and there are no unit changes involved, of course) the distance between the two places is

, which is:

(I don't see why you were trying to find an equation for

, though...)

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Bad speling makes me [sic]

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Zomg Mass Pronumerals

I see what you did. You got that equation by just translating what you were told into an equation.

Unfortunately, you used "a" for the distance that you wanted to find, when in fact a is just the distance used to find the train's speed. If you had made that a different variable, and then rearranged to find that, then you would have got the answer easily.

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Why did the vector cross the road?
It wanted to be normal.

Dross

Member

Registered: 2006-08-24

Posts: 325

Re: Zomg Mass Pronumerals

Ah, I see! I was wondering why you were after a/b... 'tis easily done!

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Bad speling makes me [sic]

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Re: Zomg Mass Pronumerals

Thanks