I do not understand...

Question

undeadknight26 · Answer

A student is running a 5-kilometer race. He runs 1 kilometer every 3 minutes. Select the function that describes his distance from the finish line.
 f(x) = - 1 over 3 x + 5

 f(x) = - 1 over 5 x + 3

 f(x) =  1 over 5 x + 5

 f(x) =  1 over 3 x + 3

definatly not the second one!

undeadknight26 · Answer

Lol long time no see splash :D

anonymous · Answer

Ok, so where is he at t=0?

anonymous · Answer

ha!

undeadknight26 · Answer

at the start.

anonymous · Answer

right--so how far away is he?

undeadknight26 · Answer

Oh wait it can't b the third one most likely is the second one...

undeadknight26 · Answer

5 kilometers...

undeadknight26 · Answer

so it would be 1/5 kilometers every 3 minutes?

undeadknight26 · Answer

1/5x + 3?

anonymous · Answer

Well, first--as time increases, you get closer to the finish line, right?

undeadknight26 · Answer

right!

anonymous · Answer

so that means that your function starts at 5 and then decreases, right?

undeadknight26 · Answer

so its -1/5?

anonymous · Answer

Well, you're right--the slope IS negative but...

undeadknight26 · Answer

-1 over 5 + 3?  meaning 1 kilometer per 3 minutes???

anonymous · Answer

Since you start out 5km away from the finish line, that means your line must have a y-intercept equal to 5

undeadknight26 · Answer

Yeah...

anonymous · Answer

So you previously said you thought it would be:

$$f(x) = 3 - \frac{ 1 }{ 5 }x$$
right?

anonymous · Answer

If that's true, how far away would you be at x = 0?

undeadknight26 · Answer

no... i said negative 1 over 5 plus 3...

anonymous · Answer

So you mean:
$$f(x) = \frac{ -1 }{ 5 }x+3$$?

anonymous · Answer

But that would mean that you're 3km from the finish at x=0 but you KNOW that you'd really be 5km away at the start...

undeadknight26 · Answer

1 over 5 negative...x + 5

anonymous · Answer

One more question:

You run 1 km every 3 minutes, right? So how far from the finish are you 3minutes into the race?

undeadknight26 · Answer

yea for 1 km...

undeadknight26 · Answer

15 minutes in all.

undeadknight26 · Answer

i ran out of time...i have 30 secs left so submitting....

anonymous · Answer

right, right. So how far from the FINISH are you after three minutes?

undeadknight26 · Answer

5/10 oh my god how many times do i redo this thing and get the same dang score!!!

undeadknight26 · Answer

*sigh* oh well thanks all...

anonymous · Answer

What are you doing, anyway?

undeadknight26 · Answer

a test...

anonymous · Answer

Anyway, the correct answer was:
$$f(x) = 5 - \frac{ 1 }{ 3 }x$$

undeadknight26 · Answer

that was not an answer...shown...

undeadknight26 · Answer

well i'll redo this soon...*sigh got one more try...

anonymous · Answer

Well, that's the same as:

$$f(x) = \frac{ -1 }{ 3 }x +5$$

anonymous · Answer

it's just a different way of writing the same thing...

undeadknight26 · Answer

well now ya tell me...lol ty any way...

anonymous · Answer

Ok, good luck!