# Rolling of two Dices!

• July 13th 2008, 08:16 PM
Vedicmaths
Rolling of two Dices!
I need help in these two problems..

Q1) Roll a pair of dice and add the two faces. What is the probability of a number that greater than 4 and at most 9?

Q2) Roll a pair of dice and add the two faces. What is the probability of an even number less than 5?

• July 13th 2008, 08:45 PM
Jhevon
Quote:

Originally Posted by Vedicmaths
I need help in these two problems..

Q1) Roll a pair of dice and add the two faces. What is the probability of a number that greater than 4 and at most 9?

Q2) Roll a pair of dice and add the two faces. What is the probability of an even number less than 5?

we can do this by drawing up a table (i hope you understand my table--the outcomes of die 1 and die 2 are in the first row and first column respectively, the other numbers are the corresponding sums):

$\begin{array}{|c|c|c|c|c|c|c|c|} \hline & \text{Die 1} & 1&2 &3 &4 &5 &6 \\
\hline \text{Die 2}& & & & & & & \\
\hline 1& &2 & 3& 4& 5& 6&7 \\
\hline 2& & 3& 4& 5& 6& 7& 8\\
\hline 3& & 4& 5& 6& 7& 8& 9\\
\hline 4& & 5& 6& 7& 8& 9& 10\\
\hline 5& & 6& 7& 8& 9& 10& 11\\
\hline 6& & 7& 8& 9& 10& 11& 12 \\
\hline
\end{array}$

now, there are 36 possible outcomes, just count the cells you want in each case, put them over 36 and that's your probability
• July 13th 2008, 10:09 PM
Vedicmaths
Sir thank you very much for your response. But I actually could not understand the problems what they are asking for?
like in problem number (1) they are asking use to figure our the probability for the sum greater than four and at most 9, so here does that mean sum should be in between 4 and five...
and In the problem (2) are they asking us to figure out the sum of the side when it hits 5? like the possibility should be (1+4) (2+2) (3+1) !...?

Thanks for the help!
• July 13th 2008, 10:39 PM
Jhevon
Quote:

Originally Posted by Vedicmaths
Sir thank you very much for your response. But I actually could not understand the problems what they are asking for?
like in problem number (1) they are asking use to figure our the probability for the sum greater than four and at most 9, so here does that mean sum should be in between 4 and five...
and In the problem (2) are they asking us to figure out the sum of the side when it hits 5? like the possibility should be (1+4) (2+2) (3+1) !...?

Thanks for the help!

Let $x$ represent the sum of the two faces.
the first problem is asking for the probability that $4 < x \le 9$. just count all the cells with numbers falling into this range and put it over 36, that's the probability
the second problem is asking for the probability that $x < 5$ and $x$ is even. so they want to know what is the probability of the sum being 2 or 4, since these are the only two cases that fulfill the condition. so just count all the cells where the sum is 2 or 4 and then put that number over 36, that's your probability