# Tutor.com Probability Session

##### Mar. 8, 2012

Session Transcript - Math - Algebra II, 3/7/2012 12:32AM - Tutor.comSession Date: 3/7/2012 12:32AM
Length: 22.4 minute(s)
Subject: Math - Algebra II

System Message
[00:00:00] *** Please note: All sessions are recorded for quality control. ***

Timothy M (Tutor)
[00:00:11] Welcome to Tutor.com ! Let's get started.

Guest (Customer)
[00:00:33] ok

Timothy M (Tutor)
[00:00:50] Can you put the problem on the board please?

Guest (Customer)
[00:01:22] um im just going to type it
[00:01:26] if thats alrite

Timothy M (Tutor)
[00:01:40] That is fine.
[00:01:42] Thanks.

Guest (Customer)
[00:02:03] ok
[00:02:43] conditioal probablity: let n be a randomly selected integer from 1 to 20 find the indicated probablity
[00:02:54] n is 2 given that it is even
[00:03:28] conditional*

Timothy M (Tutor)
[00:04:01] Okay, so how many numbers are even for integers 1 to 20?

Guest (Customer)
[00:04:14] 10

Timothy M (Tutor)
[00:04:26] Right on.
[00:04:42] Of those how many of those even numbers are 2?

Guest (Customer)
[00:04:55] 1

Timothy M (Tutor)
[00:05:17] Right on, so what is the probability that n is 2 given that it is even?

Guest (Customer)
[00:05:25] 1/10
[00:05:26] ?

Timothy M (Tutor)
[00:05:39] You got it, that is correct :-)
[00:05:49] What did we do to solve this problem?

Guest (Customer)
[00:05:48] oh ok
[00:06:43] um use dependent events
[00:06:46] ..?

Timothy M (Tutor)
[00:06:52] That is correct.
[00:07:05] We used the information we were given to determine the probability.

Guest (Customer)
[00:08:27] no

Timothy M (Tutor)
[00:08:45] Any other questions I can help with?

Guest (Customer)
[00:08:55] yeah one more thats similar

Timothy M (Tutor)
[00:09:23] Okay, if you will put the problem in the chat area.
[00:09:26] Thanks.

Guest (Customer)
[00:09:51] ok
[00:09:52] sure
[00:10:51] its the same excpet it says this time n is a prime given that it has 2 digits

Timothy M (Tutor)
[00:12:36] Any ideas on how to start this problem?

Guest (Customer)
[00:12:51] take prime numbers first

Timothy M (Tutor)
[00:13:28] Excellent, and how many of the numbers are prime?

Guest (Customer)
[00:13:35] 8

Timothy M (Tutor)
[00:14:19] Right on.
[00:14:34] What would our next step be?

Guest (Customer)
[00:15:24] to check for 2 digit num

Timothy M (Tutor)
[00:16:09] What will that give us?

Guest (Customer)
[00:16:13] 11

Timothy M (Tutor)
[00:16:33] Okay, so what will our final answer be?

Guest (Customer)
[00:16:40] 10/11
[00:16:41] ?
[00:16:49] i mean 8/11

Timothy M (Tutor)
[00:17:06] Okay. That is really close.
[00:17:17] How many prime numbers have two digits?

Guest (Customer)
[00:17:54] 4

Timothy M (Tutor)
[00:18:09] Right on, how will that change our answer?

Guest (Customer)
[00:18:21] put 8*4
[00:18:22] ?

Timothy M (Tutor)
[00:18:39] That is close.
[00:19:05] There are only 4 prime numbers that have 2 digits in our numbers from 1 to 20.
[00:19:17] So how will that change our answer?

Guest (Customer)
[00:19:44] so just put 4/11
[00:19:50] ?

Timothy M (Tutor)
[00:19:57] Right on.
[00:20:03] Why don't we use 8?

Guest (Customer)
[00:20:21] cause only 4 of those numbers are 2 digits and are prime

Timothy M (Tutor)
[00:20:33] Right on.
[00:20:46] Any questions about anything we covered tonight?

Guest (Customer)
[00:21:27] no

Timothy M (Tutor)
[00:21:42] Thanks for using Tutor.com.Â Please fill out the survey as you leave so we can learn how we can better help you in the future!Â

Guest (Customer)
[00:21:46] ok

Timothy M (Tutor)
[00:21:56] Have a nice evening.
[00:21:58] Bye.

Guest (Customer)
[00:22:00] you too
[00:22:02] bye