1)In a certain test, there are n questions .In the test 2n-1 students gave wrong answers to atleast i questions, where i=1,2,3,....n. If the total number of wrong answers given is 2047, then find the value of n.
2)A person goes in an examination where there are four papers of m marks each. The number of ways in which he can get 2m marks is?
3)A student is to answer 10 questions out of 10 in an exam such that he must choose atleast 4 from the first five questions. The number of choices available is ?(seems obv but i cant und the answer given)
answers quickly pls...
1arey had done this q longggggggggggg back i remebr d xpression bt not d xpainnation wait will post soon
1gt it ....................
no students givin xactly one wrng ansewr
2^(n-1) - 2^(n-2)
no of studnts givin wrng answer to two q's is
2^(n-2) -2^(n-3)
thus total no of ways
1(2^(n-1)-2^(n-2) +2(2^(n-2)-2^(n-3)...... + (n-1)(2-2^0)+n*1=2047
thus
2^(n-1) +2^(n-2).........+2 -n+1+n=2047
thats 2(2^(n-2) -1)/2-1 =2047
this gives n =11
62hmm.. what do i say :D
Read my comments above and the question above ;)
It should have been n-i
but king typed it as n-1
62suggest some good one?
basically this word pink works well.. (i know it is a bit girlie ;)
But pinked post kind of sounds better
62King.. check the question
should it be 2n-i (i or 1?)
otherwise the answer will be different...
Pls let me know that...
62for q3 the answer should be 1
there are 10 questions.. he has to answer all.. so the chice that he has is "fake" in many ways..
1tats wat i thot too sir but its an aiee 2003 ques and the answer is given as 196!!
The soln is given as
The no of choices available to him are:
5c4X8c6 + 5c5X8c5=196
can u pls explain this sir?
62oh the question should have been
3)A student is to answer 10 questions out of 13 in an exam such that he must choose atleast 4 from the first five questions. The number of choices available is ?
