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If John can run 9 km in y minutes , how many km can he run in 10 minutes? There are 4 options:

A) $\frac {9y} {10}$

B) $90y$

C) $\frac 1 {90y}$

D) $\frac {90} y$

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closed as off-topic by Pete L. Clark, Asaf Karagila, Adriano, tetori, Julian Kuelshammer Aug 17 '13 at 8:44

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework questions must seek to understand the concepts being taught, not just demand a solution. For help writing a good homework question, see: How to ask a homework question?." – Pete L. Clark, Asaf Karagila, Adriano, tetori, Julian Kuelshammer
If this question can be reworded to fit the rules in the help center, please edit the question.

    
Welcome to MSE! In order to get the best possible answers, especially since you have an upcoming exam, it is best to include the work that you have done to solve the above problem, as well as the particular place that you are stuck. –  Daryl Aug 17 '13 at 6:42
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If you have a math exam in two days, I'd suggest you get working, and there's no place better than this problem. Can you make any progress on it at all? –  Gerry Myerson Aug 17 '13 at 6:42
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Also, you have to write expressions so they aren't ambiguous. 1/90y could mean $(1/90)y$, or it could mean $1/(90y)$. Good idea to edit C while you're here. –  Gerry Myerson Aug 17 '13 at 6:44
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2 Answers

If he runs $9$ km in $y$ minutes, can you figure out how many kilometres he runs in $1$ minute?

Can you then figure out how many kilometres he runs in $10$ minutes?

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sorry I didn't get it –  fofo Aug 17 '13 at 6:55
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@fofo If he runs $9$ km in $3$ minutes, can you tell how many kilometres he runs in $1$ minute? –  Alraxite Aug 17 '13 at 7:00
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Hint: you don't have to use standard units, provided you are consistent - speed = distance/time could, for example, be measured in kilometres per minute.

Of course it would be much easier to help if you indicated what your problem was. Particularly when faced with an exam, you need to understand the principle of the solution so that you can answer other similar questions - this question won't be on the exam, but you need to be prepared to answer others like it.

Advice: take a deep breath and count to 5 and don't panic. Ask yourself "what do I know?" - which comes in two parts:

First: what information does the question tell me?

Second: what do I know from the course related to the question? - so here about relating distances and times

Then third - how can I use this information to make progress?

When I sit down with people before exams with this kind of question for coaching, all I do is ask them questions - very simple questions like the first and second one above, and maybe one based on the hint I've given. What I want them to do is to get the questions in their head, because when we've finished they've solved the problem. So I tell them to have confidence that they can solve such problems in an exam (after all they've just done it).

I can't do that with you and this problem - when I'm sitting next to someone I can tease out what their problem is. But I can suggest that the only way you will get prepared for the exam is to answer this problem, or another one like it, yourself.

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sorry I didn't get it –  fofo Aug 17 '13 at 6:56
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@fofo What didn't you get? Do you know how to relate distance, time and speed so that if you know two of these you can calculate the third? –  Mark Bennet Aug 17 '13 at 7:06
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