Combinatorics

13/03/2016

Find the sum of all distinct four digit numbers that can be formed
using the digits 1, 2, 3, 4, 5, each digit appearing at most once.

13/01/2016

Determine the number of 3-digit numbers in base 10 having at least one 5 and at most one 3.
Ans: 249

09/01/2016

Find the sum of all 3-digit natural numbers which contain at least one odd digit and at least one even digit.
Ans: 370775

23/08/2015

Let n be the number of ways in which 5 boys and 5 girls can stand in a queue in such a way that all the girls stand consecutively in the queue. Let m be the number of ways in which 5 boys and 5 girls can stand in a queue in such a way that exactly four girls stand consecutively in the queue. Then the value of m/n is ?
ANSWER: 5

10/06/2015

Let S={(a1,a2,a3)}| 0≤ ai ≤ 9 and a1+a2+a3 isdivisibleby3}. Find the number of elements in S.

27/05/2015

Using only the digits 2, 3 and 9, how many six digit numbers can be formed which are divisible by 6?
http://mathsvinu.blogspot.in/2015/05/indian-statistical-institute.html

23/05/2015

Indian Statistical Institute
http://mathsvinu.blogspot.com/2015/05/combinatorics-indian-statistical.html

11/04/2015

Counting under restriction.

10/04/2015

The number of points, having both co-ordinates as integers, that lie in the interior of the triangle with vertices (0,0), (0,41) and (41,0), is:
1) 861
2) 820
3) 780
4) 901

23/12/2014

A five digit number divisible by 3 is to be formed using the digits 0,1,2,3,4 and 5 without repetition. find the total number of ways this can be done.

14/12/2014

06/12/2014