# PnC : Summing Up

## 6 thoughts on “PnC : Summing Up”

1. Gaurav |

Sorry to post this question in random thread…But since its quite relevant I m posting It..

Answer the questions independently of each other.

There are 12 points in a plane, out of which only four are collinear and the remaining eight are non-collinear. How many non-overlapping straight line segment can be drawn by joining any two of these points?
Actually I got two different solution within IMS Test papers..

2. Lines will give a different answer, and non-overlapping line segments will give a different answer. Be careful.

regards
J

3. Saurabh |

Thank you for the entire PnC thread! It was a lot of fun going through it and it helped me a lot! ðŸ™‚

4. Siddharth Sekhar |

Sir,
In the formula for type where we distribute ‘x’ distinct objects into ‘y’ distinct groups AND there is arrangement within groups, shouldn’t it read ” Send n distinct objects to r distinct groups”,
since the answer is P(n+r-1, n) ?

5. Tanmay |

Sir, in the 6th case of arranging r out of n in circle…can we do it by first selecting r out of n, then arranging them in (r-1)! ways…so nCr*(r-1)!……?

• I don’t think that would work; the n are not distinct to begin with. In the situation, I meant n positions and r (<=n) people to be arranged in them, I think what you are saying would work fine for n people and r positions. Sorry for the ambiguity!

regards
J