Questionbank: Permutation and Probability

You are here: Home  CAT Questionbank   CAT Quant  Permutation and Probability  Question 28
Clue - FInd the number of rearrangements and then focus on the number of digits

Sum of Rearrangements

    Q.28: Of 22 points on a plane, 8 are on a straight line, 7 are on another straight line and 10 are on a third straight line. How many triangles can be drawn by connecting some two points from these 22?
    1. 22C3
    2. 22C3 - (8C3+ 7C3 +10C3)
    3. 22C3 + (8C3+ 7C3 +10C3)
    4. 8C3+ 7C3 +10C3

 

  • Correct Answer
    Choice B. 22C3 - (8C3+ 7C3 +10C3)

Detailed Solution

From the 22 points on a plane we can form 22C3 triangles but it is given that 8 are on one straight line, 7 are on another straight line and 10 more are on another straight line, so we can form triangles on joining points which are on straight lines so we have to subtract (8C3+ 7C3 +10C3) from the total.

Hence, we can form 22C3 - (8C3+ 7C3 +10C3) triangles.

Correct Answer : 22C3 - (8C3+ 7C3 +10C3)

Our Online Course, Now on Google Playstore!

2IIM's App

Fully Functional Course on Mobile

All features of the online course, including the classes, discussion board, quizes and more, on a mobile platform.


Cache Content for Offline Viewing

Download videos onto your mobile so you can learn on the fly, even when the network gets choppy!

Get it on Google Play
Visit Piverb.com
Visit Wizako.com