MA Economics Entrance Coaching › Forums › Subject forums › Math › permutation and combination
Tagged: engineering module
This topic contains 5 replies, has 3 voices, and was last updated by rohit pandey 3 years, 8 months ago.

AuthorPosts

August 11, 2014 at 12:15 pm #525
q1 a seven digit no divisible by 9 is to be formed by using 7 no’s out of {1,2,3,4,5,6,7,8,9} the no of ways in which this can be done is? final ans:4*7!
q2 the no f ways in which 3 girls and 3 boys all of diff heights be arranged in a line so tht the boys as well as girls among themselves are arranged in decreasing order of their heights(frm left to right)?
final ans:20
shruti290Quote 
August 12, 2014 at 7:52 am #542
shruti the answer for q2 is indeed 20 but i will have to explain it in class.hint try forming a tree its really big.
and for q1 if you take and sum the different permutations of 7 numbers form set you will find the sum of 4 options is divisible by 9 hence 4*7!.
rohit pandeyQuote 
August 13, 2014 at 12:56 pm #554
this is if first choice is g1 which has ten ways now for b1 also there willbe 10 ways.
rohit pandeyQuote 
AuthorPosts
You must be logged in to reply to this topic.