There are 20 intermediate stations on a track,a train has to stop at any 4 stations
In how many ways the train can stop?

Question

There are 20 intermediate stations on a track,a train has to stop at any 4 stations
In how many ways the train can stop?

dls · Answer

@agent0smith

ghostfire · Answer

I think it would be 
$$20\times19\times18\times17$$
ways the train can stop

dls · Answer

Nah.

anonymous · Answer

20 C 4

dls · Answer

Nah.

shubhamsrg · Answer

C(20,4) seems fine to me, unless I am misinterpreting the question .

agent0smith · Answer

I don't see how it's not 20C4. From 20 train stations, choose 4...

dls · Answer

I don't see how its 20C4

dls · Answer

w+x+y+z=20
w>1,x>1,y>1,z>1
n-1Cr-1
19C3  is the answer

yrelhan4 · Answer

w>1,x>1,y>1,z>1 Explain?

dls · Answer

if i knew the explanation i wouldn't post it XD

yrelhan4 · Answer

^ Best response.

agent0smith · Answer

@DLS ... from 20 stations, the train must choose 4 to stop at. 20C4 means = from 20, choose 4.

agent0smith · Answer

There are 20 intermediate stations on a track,a train has to stop at any 4 stations
In how many ways the train can stop?

17C3 means = from 17 stations, choose three to stop at.

dls · Answer

19C3,it is

agent0smith · Answer

w+x+y+z=20
w>1,x>1,y>1,z>1
n-1Cr-1
19C3  is the answer

this is pretty  odd. wtf are w, x, y and z supposed to be? It's not stopping at a minimum of 4 stations, it's stopping at exactly 4.

dls · Answer

What if no 2 stopping stations are consecutive

agent0smith · Answer

The question doesn't state that though. As is, the answer should be 20C4. It literally means, from 20 stations choose 4... exactly as the question states.

agent0smith · Answer

If they are not consecutive, then: http://openstudy.com/study#/updates/4f1f43cae4b076dbc3482936

yrelhan4 · Answer

Its should be 20c4 @agent0smith . But sometimes these questions are a bit tricky and i'm still open for the answer not being 20c4.

agent0smith · Answer

Maybe it's the definition of an intermediate station: http://dictionary.reverso.net/english-cobuild/intermediate%20station

yrelhan4 · Answer

So is w>1,x>1,y>1,z>1 making sense? This must mean that no two stations are consecutive?

yrelhan4 · Answer

Nope it isnt making sense.

agent0smith · Answer

Maybe intermediate means it can't stop at two consecutive stations, and w, x, y, z are the number of stations it skips from one to the next.

eg:

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