become expert | help | login
refer a friend - earn nickels!!
 advanced

  Ask & Discuss Questions with Community & Experts

 Moderation Team
  500 chars left
Ask community Community Discussion Question: Combination
Reply Forum Index -> Algebra originally posted here on IIT-JEE / AIEEE community   
Email  
Author Message
[Post New] 5 Feb 2012 18:08:00 IST
   Subject: A student is allowed to select at most n books from a collection of (2n+1) books. If the total n
[Up] View Post
Siddhant chaudhary (0)

Cool IASian

Olaaa!! Perrrfect answer. 0  [0 rates]
Siddhant chaudhary's Avatar
total posts: 84    
Offline
A student is allowed to select at most n books from a collection of (2n+1) books. If the total number of ways in which he can select a book is 63 . Find the value of n .
    
[Post New] 5 Feb 2012 18:42:23 IST
   Subject: Combination
[Up] View Post
Vishal U. Karve (205)

Hot IASian

Olaaa!! Perrrfect answer. 41  [41 rates]
Vishal U. Karve's Avatar
total posts: 147    
Offline

2n+1C1+2n+1C2+...+2n+1Cn is the required no. of ways.

Simplifying...

=1/2 [2n+1C1+2n+1C2+...+2n+1C2n]

=1/2[22n+1-2]

=22n-1

Given,

22n-1=63

22n=64

22n=26

n=3
Knowledge is power.
  this reply:   0 points  (with 0  Olaaa!! Perrrfect answer.   in 0   votes   )     [?]
 
You have to be logged on to rate
  
 
reply Forum Index -> Algebra
Go to: 
Sponsored Links
preparing for IAS ?
Brilliant Tutorial's correspondence
Complete course. Buy Online Now !
goiit.com/Brilliant-UPSC-postal

preparing for IAS ?
free online tests
Complete course. FREE Analysis !
go4ias.com/ACCELERATE

Preparing for IES ?
Brilliant Tutorial's correspondence
full course prep. Buy Online !
goiit.com/brilliant-IES

preparing for BSNL JTO ?
solved, model paper, rank predictor
online, study material. Buy Online!
go4ias.com/BSNL-JTO

preparing GATE 2010?
solved, model Papers,study Material
courses from Brilliant. Buy Now !
goiit.com/Brilliant-GATE