counting

Question

In an experiment 4 different colored dice are thrown simultaneously and numbers are added find number of distinct experiments such that total is 18?

Answer 1

We require the no of solution of the equation  X1+X2+X3+X4=18 where 1<=X1,X2,X3,X4<=6.
You have form  all non increasing solution of the above eq and permuate them.

Non increasing order of solution	No of permutation possible for this solution
6 6 5 1	12
6 6 4 2	12
6 6 3 3	6
6 5 4 3	24
6 5 2 5	12
6 4 4 4	4
5 5 4 4	6
5 5 5 3	4
Total	80

This method is brute force method and its highly prone to careless mistake.
For ans verification you can write a simple programe(https://ideone.com/E9Vym3)

Comments

i am getting answer as 52

Answer 2

http://math.stackexchange.com/questions/992125/rolling-dice-problem

i used this technique!

Comments

thank u for the link.. :)