A friend comes to other and says can u do me a favour pick letters randomly from the stack such that all the letters that u pick are 5% of the total letters. The other friend while sorting just picked up letter number one, missed one, picked up another letter, missed two picked one letter ,missed three, picked another letter, and so on...till he picked last letter to his amazement he found that the picked up letters were 5% of the total letters in the stack. How many letters did he pick?

Ans: 39

tulasij
Profile Answers by tulasij Questions by tulasij
Mar 17th, 2006
4
1250

Showing Answers 1 - 4 of 4 Answers

Deepal Udeshi

Apr 1st, 2006

hi could you please tell me how you got this answer
newys thanks

sunil_dalvi82
Profile Answers by sunil_dalvi82 Questions by sunil_dalvi82

Apr 3rd, 2006

Let the total number of cards removed be n, thus the total number of cards in the pack is sum of series (1,2,3,..n).Sum of this series is (n)(n-1)/2. thus equating (we know cards removed is 5% of total cards)we get n=39.

dhiraj

Apr 30th, 2006

picked :- 1 1 1 1 1 1 1 1 1 1.........n
missed:-1 2 3 4 5......................n
sum of missed= n(n+1)/2
[ n+n(n+1)/2]*5%=n (i.e.the 5%of( picked+missed)=picked)
n=37

Arun

Jun 10th, 2006

ans - 39 total cards - 1 2 3 4 5 6 7 8 9 10....no of cards picked - 1 2 3 4....so total no of cards = n (n+1) where n is no of cards picked ---------- 2then 5 % of total no of cards = [n(n+1)/2] [5/100] = n so n = 39