The 10 stations...
Probability
Level
3
Before P and Q there are 10 intermediate stations . The number of ways in which a train can be made to stop at 4 of these stations so that no two of these halting stations are consecutive
The answer is 35.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
Consider the illustration: _ x _ x _ x _ x _ x _ x _
where the x's represent stations for which the train didn't halt. To make sure no two halting stations are consecutive, we only choose 4 of the 7 underscores ( _ ), C(7,4) = 35.